diff --git a/include/zephyr/net/lwm2m.h b/include/zephyr/net/lwm2m.h
index 3fca8bffae3..c643c32f0bf 100644
--- a/include/zephyr/net/lwm2m.h
+++ b/include/zephyr/net/lwm2m.h
@@ -1009,11 +1009,16 @@ int lwm2m_engine_set_u64(const char *pathstr, uint64_t value);
 /**
  * @brief Set resource (instance) value (u64)
  *
+ * @deprecated Unsigned 64bit value type does not exits.
+ *             This is internally handled as a int64_t.
+ *             Use lwm2m_set_s64() instead.
+ *
  * @param[in] path LwM2M path as a struct
  * @param[in] value u64 value
  *
  * @return 0 for success or negative in case of error.
  */
+__deprecated
 int lwm2m_set_u64(const struct lwm2m_obj_path *path, uint64_t value);
 
 /**
@@ -1335,11 +1340,16 @@ int lwm2m_engine_get_u64(const char *pathstr, uint64_t *value);
 /**
  * @brief Get resource (instance) value (u64)
  *
+ * @deprecated Unsigned 64bit value type does not exits.
+ *             This is internally handled as a int64_t.
+ *             Use lwm2m_get_s64() instead.
+
  * @param[in] path LwM2M path as a struct
  * @param[out] value u64 buffer to copy data into
  *
  * @return 0 for success or negative in case of error.
  */
+__deprecated
 int lwm2m_get_u64(const struct lwm2m_obj_path *path, uint64_t *value);
 
 /**
diff --git a/subsys/net/lib/lwm2m/lwm2m_registry.c b/subsys/net/lib/lwm2m/lwm2m_registry.c
index 210c5525756..1701b7f7412 100644
--- a/subsys/net/lib/lwm2m/lwm2m_registry.c
+++ b/subsys/net/lib/lwm2m/lwm2m_registry.c
@@ -890,7 +890,7 @@ int lwm2m_engine_set_u64(const char *pathstr, uint64_t value)
 	if (ret < 0) {
 		return ret;
 	}
-	return lwm2m_set_u64(&path, value);
+	return lwm2m_set_s64(&path, (int64_t) value);
 }
 
 int lwm2m_set_s8(const struct lwm2m_obj_path *path, int8_t value)
@@ -1378,7 +1378,7 @@ int lwm2m_engine_get_u64(const char *pathstr, uint64_t *value)
 	if (ret < 0) {
 		return ret;
 	}
-	return lwm2m_get_u64(&path, value);
+	return lwm2m_get_s64(&path, (int64_t *) value);
 }
 
 int lwm2m_get_s8(const struct lwm2m_obj_path *path, int8_t *value)
diff --git a/subsys/net/lib/lwm2m/lwm2m_shell.c b/subsys/net/lib/lwm2m/lwm2m_shell.c
index 5dc891178ff..13f38fefe66 100644
--- a/subsys/net/lib/lwm2m/lwm2m_shell.c
+++ b/subsys/net/lib/lwm2m/lwm2m_shell.c
@@ -246,14 +246,6 @@ static int cmd_read(const struct shell *sh, size_t argc, char **argv)
 			goto out;
 		}
 		shell_print(sh, "%d\n", temp);
-	} else if (strcmp(dtype, "-u64") == 0) {
-		uint64_t temp = 0;
-
-		ret = lwm2m_get_u64(&path, &temp);
-		if (ret != 0) {
-			goto out;
-		}
-		shell_print(sh, "%lld\n", temp);
 	} else if (strcmp(dtype, "-f") == 0) {
 		double temp = 0;
 
@@ -349,8 +341,6 @@ static int cmd_write(const struct shell *sh, size_t argc, char **argv)
 			ret = lwm2m_set_u16(&path, strtoul(value, &e, 10));
 		} else if (strcmp(dtype, "-u32") == 0) {
 			ret = lwm2m_set_u32(&path, strtoul(value, &e, 10));
-		} else if (strcmp(dtype, "-u64") == 0) {
-			ret = lwm2m_set_u64(&path, strtoull(value, &e, 10));
 		} else if (strcmp(dtype, "-b") == 0) {
 			ret = lwm2m_set_bool(&path, strtoul(value, &e, 10));
 		} else if (strcmp(dtype, "-t") == 0) {
diff --git a/tests/net/lib/lwm2m/lwm2m_registry/src/lwm2m_registry.c b/tests/net/lib/lwm2m/lwm2m_registry/src/lwm2m_registry.c
index d4c0a7757a6..8e99f666b7f 100644
--- a/tests/net/lib/lwm2m/lwm2m_registry/src/lwm2m_registry.c
+++ b/tests/net/lib/lwm2m/lwm2m_registry/src/lwm2m_registry.c
@@ -203,16 +203,6 @@ ZTEST(lwm2m_registry, test_get_set)
 	zassert_equal(strlen(buf), 0);
 }
 
-ZTEST(lwm2m_registry, test_missing_u64)
-{
-	/* This data type is missing, so use S64 resource instead */
-	uint64_t u64 = 123;
-
-	zassert_equal(lwm2m_set_u64(&LWM2M_OBJ(32768, 0, LWM2M_RES_TYPE_S64), u64), 0);
-	zassert_equal(lwm2m_get_u64(&LWM2M_OBJ(32768, 0, LWM2M_RES_TYPE_S64), &u64), 0);
-	zassert_equal(u64, 123);
-}
-
 ZTEST(lwm2m_registry, test_temp_sensor)
 {
 	int ret;