diff --git a/subsys/net/lib/lwm2m/lwm2m_engine.c b/subsys/net/lib/lwm2m/lwm2m_engine.c
index 92d5081b3b4..194b45c92ff 100644
--- a/subsys/net/lib/lwm2m/lwm2m_engine.c
+++ b/subsys/net/lib/lwm2m/lwm2m_engine.c
@@ -138,18 +138,7 @@ static int sock_nfds;
 /* TODO: figure out what's correct value */
 #define TIMEOUT_BLOCKWISE_TRANSFER_MS (MSEC_PER_SEC * 30)
 
-struct block_context {
-	struct coap_block_context ctx;
-	int64_t timestamp;
-	uint32_t remaining_len;
-	uint32_t expected;
-	uint8_t token[8];
-	uint8_t tkl;
-	uint8_t opaque_header_len;
-	bool last_block : 1;
-};
-
-static struct block_context block1_contexts[NUM_BLOCK1_CONTEXT];
+static struct lwm2m_block_context block1_contexts[NUM_BLOCK1_CONTEXT];
 
 /* write-attribute related definitons */
 static const char * const LWM2M_ATTR_STR[] = { "pmin", "pmax",
@@ -243,8 +232,8 @@ enum coap_block_size lwm2m_default_block_size(void)
 	return COAP_BLOCK_256;
 }
 
-static int
-init_block_ctx(const uint8_t *token, uint8_t tkl, struct block_context **ctx)
+static int init_block_ctx(const uint8_t *token, uint8_t tkl,
+			  struct lwm2m_block_context **ctx)
 {
 	int i;
 	int64_t timestamp;
@@ -276,16 +265,15 @@ init_block_ctx(const uint8_t *token, uint8_t tkl, struct block_context **ctx)
 	memcpy((*ctx)->token, token, tkl);
 	coap_block_transfer_init(&(*ctx)->ctx, lwm2m_default_block_size(), 0);
 	(*ctx)->timestamp = timestamp;
-	(*ctx)->remaining_len = 0;
-	(*ctx)->opaque_header_len = 0;
 	(*ctx)->expected = 0;
 	(*ctx)->last_block = false;
+	memset(&(*ctx)->opaque, 0, sizeof((*ctx)->opaque));
 
 	return 0;
 }
 
-static int
-get_block_ctx(const uint8_t *token, uint8_t tkl, struct block_context **ctx)
+static int get_block_ctx(const uint8_t *token, uint8_t tkl,
+			 struct lwm2m_block_context **ctx)
 {
 	int i;
 
@@ -308,7 +296,7 @@ get_block_ctx(const uint8_t *token, uint8_t tkl, struct block_context **ctx)
 	return 0;
 }
 
-static void free_block_ctx(struct block_context *ctx)
+static void free_block_ctx(struct lwm2m_block_context *ctx)
 {
 	if (ctx == NULL) {
 		return;
@@ -2213,9 +2201,11 @@ static int lwm2m_read_handler(struct lwm2m_engine_obj_inst *obj_inst,
 }
 
 size_t lwm2m_engine_get_opaque_more(struct lwm2m_input_context *in,
-				    uint8_t *buf, size_t buflen, bool *last_block)
+				    uint8_t *buf, size_t buflen,
+				    struct lwm2m_opaque_context *opaque,
+				    bool *last_block)
 {
-	uint32_t in_len = in->opaque_len;
+	uint32_t in_len = opaque->remaining;
 	uint16_t remaining = in->in_cpkt->max_len - in->offset;
 
 	if (in_len > buflen) {
@@ -2226,9 +2216,9 @@ size_t lwm2m_engine_get_opaque_more(struct lwm2m_input_context *in,
 		in_len = remaining;
 	}
 
-	in->opaque_len -= in_len;
+	opaque->remaining -= in_len;
 	remaining -= in_len;
-	if (in->opaque_len == 0U || remaining == 0) {
+	if (opaque->remaining == 0U || remaining == 0) {
 		*last_block = true;
 	}
 
@@ -2245,80 +2235,44 @@ static int lwm2m_write_handler_opaque(struct lwm2m_engine_obj_inst *obj_inst,
 				      struct lwm2m_engine_res *res,
 				      struct lwm2m_engine_res_inst *res_inst,
 				      struct lwm2m_input_context *in,
-				      void *data_ptr, size_t data_len,
-				      struct block_context *block_ctx)
+				      void *data_ptr, size_t data_len)
 {
 	size_t len = 1;
-	bool last_pkt_block = false, first_read = true;
-	int block_num = 0;
+	bool last_pkt_block = false;
 	int ret = 0;
-	size_t total_size = 0;
 	bool last_block = true;
+	struct lwm2m_opaque_context opaque_ctx = { 0 };
 
-	if (block_ctx != NULL) {
-		block_num = block_ctx->ctx.current /
-			coap_block_size_to_bytes(block_ctx->ctx.block_size);
-		last_block = block_ctx->last_block;
+	if (in->block_ctx != NULL) {
+		last_block = in->block_ctx->last_block;
+
+		/* Restore the opaque context from the block context, if used.
+		*/
+		opaque_ctx = in->block_ctx->opaque;
 	}
 
 	while (!last_pkt_block && len > 0) {
-		if (first_read && block_num == 0) {
-			len = engine_get_opaque(in, (uint8_t *)data_ptr,
-						data_len, &last_pkt_block);
-			if (len == 0) {
-				/* ignore empty content and continue */
-				return 0;
-			}
-
-			if (block_ctx != NULL) {
-				block_ctx->remaining_len = in->opaque_len;
-				/* engine_get_opaque returns only the actual
-				 * data length, not the header length, so we
-				 * need to calculate it.
-				 */
-				block_ctx->opaque_header_len =
-					block_ctx->ctx.total_size -
-					(block_ctx->remaining_len + len);
-			}
-
-			first_read = false;
-		} else {
-			if (block_ctx != NULL) {
-				in->opaque_len = block_ctx->remaining_len;
-			}
-
-			len = lwm2m_engine_get_opaque_more(in, (uint8_t *)data_ptr,
-							   data_len,
-							   &last_pkt_block);
-
-			if (block_ctx != NULL) {
-				block_ctx->remaining_len = in->opaque_len;
-			}
-		}
-
+		len = engine_get_opaque(in, (uint8_t *)data_ptr,
+					data_len, &opaque_ctx, &last_pkt_block);
 		if (len == 0) {
-			return -EINVAL;
+			/* ignore empty content and continue */
+			return 0;
 		}
-
-		if (block_ctx != NULL) {
-			/* We shall only report the actual total data length,
-			 * excluding the header size (if any).
-			 */
-			total_size = block_ctx->ctx.total_size -
-				     block_ctx->opaque_header_len;
-		}
-
 		if (res->post_write_cb) {
 			ret = res->post_write_cb(
 				obj_inst->obj_inst_id, res->res_id,
 				res_inst->res_inst_id, data_ptr, len,
-				last_pkt_block && last_block, total_size);
+				last_pkt_block && last_block, opaque_ctx.len);
 			if (ret < 0) {
 				return ret;
 			}
 		}
 	}
 
+	if (in->block_ctx != NULL) {
+		in->block_ctx->opaque = opaque_ctx;
+	}
+
 	return ret;
 }
 
@@ -2329,7 +2283,6 @@ int lwm2m_write_handler(struct lwm2m_engine_obj_inst *obj_inst,
 			struct lwm2m_engine_obj_field *obj_field,
 			struct lwm2m_message *msg)
 {
-	struct block_context *block_ctx = NULL;
 	void *data_ptr = NULL;
 	size_t data_len = 0;
 	size_t len = 0;
@@ -2337,8 +2290,6 @@ int lwm2m_write_handler(struct lwm2m_engine_obj_inst *obj_inst,
 	int64_t temp64 = 0;
 	int32_t temp32 = 0;
 	int ret = 0;
-	uint8_t token[8];
-	uint8_t tkl = 0U;
 	bool last_block = true;
 
 	if (!obj_inst || !res || !res_inst || !obj_field || !msg) {
@@ -2361,19 +2312,14 @@ int lwm2m_write_handler(struct lwm2m_engine_obj_inst *obj_inst,
 	}
 
 	if (res->post_write_cb) {
-		/* Get block1 option for checking MORE block flag */
-		ret = coap_get_option_int(msg->in.in_cpkt, COAP_OPTION_BLOCK1);
-		if (ret >= 0) {
+		if (msg->in.block_ctx != NULL) {
 			/* Get block_ctx for total_size (might be zero) */
-			tkl = coap_header_get_token(msg->in.in_cpkt, token);
-			if (tkl && !get_block_ctx(token, tkl, &block_ctx)) {
-				total_size = block_ctx->ctx.total_size;
-				LOG_DBG("BLOCK1: total:%zu current:%zu"
-					" last:%u",
-					block_ctx->ctx.total_size,
-					block_ctx->ctx.current,
-					block_ctx->last_block);
-			}
+			total_size = msg->in.block_ctx->ctx.total_size;
+			LOG_DBG("BLOCK1: total:%zu current:%zu"
+				" last:%u",
+				msg->in.block_ctx->ctx.total_size,
+				msg->in.block_ctx->ctx.current,
+				msg->in.block_ctx->last_block);
 		}
 	}
 
@@ -2383,8 +2329,7 @@ int lwm2m_write_handler(struct lwm2m_engine_obj_inst *obj_inst,
 		case LWM2M_RES_TYPE_OPAQUE:
 			ret = lwm2m_write_handler_opaque(obj_inst, res,
 							 res_inst, &msg->in,
-							 data_ptr, data_len,
-							 block_ctx);
+							 data_ptr, data_len);
 			if (ret < 0) {
 				return ret;
 			}
@@ -3330,7 +3275,7 @@ static int handle_request(struct coap_packet *request,
 	int observe = -1; /* default to -1, 0 = ENABLE, 1 = DISABLE */
 	bool well_known = false;
 	int block_opt, block_num;
-	struct block_context *block_ctx = NULL;
+	struct lwm2m_block_context *block_ctx = NULL;
 	enum coap_block_size block_size;
 	uint16_t payload_len = 0U;
 	bool last_block = false;
@@ -3543,6 +3488,8 @@ static int handle_request(struct coap_packet *request,
 			goto error;
 		}
 
+		msg->in.block_ctx = block_ctx;
+
 		if (block_num < block_ctx->expected) {
 			LOG_WRN("Block already handled %d, expected %d",
 				block_num, block_ctx->expected);
@@ -4518,8 +4465,7 @@ static int lwm2m_engine_init(const struct device *dev)
 {
 	int ret = 0;
 
-	(void)memset(block1_contexts, 0,
-		     sizeof(struct block_context) * NUM_BLOCK1_CONTEXT);
+	(void)memset(block1_contexts, 0, sizeof(block1_contexts));
 
 	/* start sock receive thread */
 	k_thread_create(&engine_thread_data,
diff --git a/subsys/net/lib/lwm2m/lwm2m_engine.h b/subsys/net/lib/lwm2m/lwm2m_engine.h
index 94fe10993b4..9c55e17edfc 100644
--- a/subsys/net/lib/lwm2m/lwm2m_engine.h
+++ b/subsys/net/lib/lwm2m/lwm2m_engine.h
@@ -102,7 +102,9 @@ int lwm2m_engine_get_resource(char *pathstr,
 void lwm2m_engine_get_binding(char *binding);
 
 size_t lwm2m_engine_get_opaque_more(struct lwm2m_input_context *in,
-				    uint8_t *buf, size_t buflen, bool *last_block);
+				    uint8_t *buf, size_t buflen,
+				    struct lwm2m_opaque_context *opaque,
+				    bool *last_block);
 
 int lwm2m_security_inst_id_to_index(uint16_t obj_inst_id);
 int lwm2m_security_index_to_inst_id(int index);
diff --git a/subsys/net/lib/lwm2m/lwm2m_object.h b/subsys/net/lib/lwm2m/lwm2m_object.h
index 444fd6deec9..ef5955ab965 100644
--- a/subsys/net/lib/lwm2m/lwm2m_object.h
+++ b/subsys/net/lib/lwm2m/lwm2m_object.h
@@ -363,6 +363,21 @@ static inline void init_res_instance(struct lwm2m_engine_res_inst *ri,
 	}
 }
 
+struct lwm2m_opaque_context {
+	size_t len;
+	size_t remaining;
+};
+
+struct lwm2m_block_context {
+	struct coap_block_context ctx;
+	struct lwm2m_opaque_context opaque;
+	int64_t timestamp;
+	uint32_t expected;
+	uint8_t token[8];
+	uint8_t tkl;
+	bool last_block : 1;
+};
+
 struct lwm2m_output_context {
 	const struct lwm2m_writer *writer;
 	struct coap_packet *out_cpkt;
@@ -378,8 +393,8 @@ struct lwm2m_input_context {
 	/* current position in buffer */
 	uint16_t offset;
 
-	/* length of incoming opaque */
-	size_t opaque_len;
+	/* Corresponding block context. NULL if block transfer is not used. */
+	struct lwm2m_block_context *block_ctx;
 
 	/* private output data */
 	void *user_data;
@@ -490,7 +505,9 @@ struct lwm2m_reader {
 	size_t (*get_bool)(struct lwm2m_input_context *in,
 			   bool *value);
 	size_t (*get_opaque)(struct lwm2m_input_context *in,
-			     uint8_t *buf, size_t buflen, bool *last_block);
+			     uint8_t *buf, size_t buflen,
+			     struct lwm2m_opaque_context *opaque,
+			     bool *last_block);
 	size_t (*get_objlnk)(struct lwm2m_input_context *in,
 			     struct lwm2m_objlnk *value);
 };
@@ -725,10 +742,12 @@ static inline size_t engine_get_bool(struct lwm2m_input_context *in,
 
 static inline size_t engine_get_opaque(struct lwm2m_input_context *in,
 				       uint8_t *buf, size_t buflen,
+				       struct lwm2m_opaque_context *opaque,
 				       bool *last_block)
 {
 	if (in->reader->get_opaque) {
-		return in->reader->get_opaque(in, buf, buflen, last_block);
+		return in->reader->get_opaque(in, buf, buflen,
+					      opaque, last_block);
 	}
 
 	return 0;
diff --git a/subsys/net/lib/lwm2m/lwm2m_rw_json.c b/subsys/net/lib/lwm2m/lwm2m_rw_json.c
index 00996e6b4ae..bd905f4feda 100644
--- a/subsys/net/lib/lwm2m/lwm2m_rw_json.c
+++ b/subsys/net/lib/lwm2m/lwm2m_rw_json.c
@@ -684,7 +684,9 @@ static size_t get_bool(struct lwm2m_input_context *in, bool *value)
 }
 
 static size_t get_opaque(struct lwm2m_input_context *in,
-			 uint8_t *value, size_t buflen, bool *last_block)
+			 uint8_t *value, size_t buflen,
+			 struct lwm2m_opaque_context *opaque,
+			 bool *last_block)
 {
 	/* TODO */
 	return 0;
diff --git a/subsys/net/lib/lwm2m/lwm2m_rw_oma_tlv.c b/subsys/net/lib/lwm2m/lwm2m_rw_oma_tlv.c
index 18fbe74bb04..0652be9ff15 100644
--- a/subsys/net/lib/lwm2m/lwm2m_rw_oma_tlv.c
+++ b/subsys/net/lib/lwm2m/lwm2m_rw_oma_tlv.c
@@ -758,13 +758,23 @@ static size_t get_bool(struct lwm2m_input_context *in, bool *value)
 }
 
 static size_t get_opaque(struct lwm2m_input_context *in,
-			 uint8_t *value, size_t buflen, bool *last_block)
+			 uint8_t *value, size_t buflen,
+			 struct lwm2m_opaque_context *opaque,
+			 bool *last_block)
 {
 	struct oma_tlv tlv;
+	size_t size;
 
-	oma_tlv_get(&tlv, in, false);
-	in->opaque_len = tlv.length;
-	return lwm2m_engine_get_opaque_more(in, value, buflen, last_block);
+	/* Get the TLV header only on first read. */
+	if (opaque->remaining == 0) {
+		size = oma_tlv_get(&tlv, in, false);
+
+		opaque->len = tlv.length;
+		opaque->remaining = tlv.length;
+	}
+
+	return lwm2m_engine_get_opaque_more(in, value, buflen,
+					    opaque, last_block);
 }
 
 static size_t get_objlnk(struct lwm2m_input_context *in,
diff --git a/subsys/net/lib/lwm2m/lwm2m_rw_plain_text.c b/subsys/net/lib/lwm2m/lwm2m_rw_plain_text.c
index d1c54461e01..23aeff14712 100644
--- a/subsys/net/lib/lwm2m/lwm2m_rw_plain_text.c
+++ b/subsys/net/lib/lwm2m/lwm2m_rw_plain_text.c
@@ -202,11 +202,6 @@ static size_t put_objlnk(struct lwm2m_output_context *out,
 				     value->obj_inst);
 }
 
-static int get_length_left(struct lwm2m_input_context *in)
-{
-	return in->in_cpkt->offset - in->offset;
-}
-
 static size_t plain_text_read_number(struct lwm2m_input_context *in,
 				     int64_t *value1,
 				     int64_t *value2,
@@ -275,7 +270,9 @@ static size_t get_s64(struct lwm2m_input_context *in, int64_t *value)
 static size_t get_string(struct lwm2m_input_context *in,
 			 uint8_t *value, size_t buflen)
 {
-	uint16_t in_len = get_length_left(in);
+	uint16_t in_len;
+
+	coap_packet_get_payload(in->in_cpkt, &in_len);
 
 	if (in_len > buflen) {
 		/* TODO: generate warning? */
@@ -332,10 +329,43 @@ static size_t get_bool(struct lwm2m_input_context *in,
 }
 
 static size_t get_opaque(struct lwm2m_input_context *in,
-			 uint8_t *value, size_t buflen, bool *last_block)
+			 uint8_t *value, size_t buflen,
+			 struct lwm2m_opaque_context *opaque,
+			 bool *last_block)
 {
-	in->opaque_len = get_length_left(in);
-	return lwm2m_engine_get_opaque_more(in, value, buflen, last_block);
+	uint16_t in_len;
+
+	if (opaque->remaining == 0) {
+		coap_packet_get_payload(in->in_cpkt, &in_len);
+
+		if (in->block_ctx != NULL) {
+			uint32_t block_num =
+				in->block_ctx->ctx.current /
+				coap_block_size_to_bytes(
+					in->block_ctx->ctx.block_size);
+
+			if (block_num == 0) {
+				opaque->len = in->block_ctx->ctx.total_size;
+			}
+
+			if (opaque->len == 0) {
+				/* No size1 option provided, use current
+				 * payload size. This will reset on next packet
+				 * received.
+				 */
+				opaque->remaining = in_len;
+			} else {
+				opaque->remaining = opaque->len;
+			}
+
+		} else {
+			opaque->len = in_len;
+			opaque->remaining = in_len;
+		}
+	}
+
+	return lwm2m_engine_get_opaque_more(in, value, buflen,
+					    opaque, last_block);
 }