diff --git a/kernel/mempool.c b/kernel/mempool.c
index 08bc7650e0c..ecc59a87c46 100644
--- a/kernel/mempool.c
+++ b/kernel/mempool.c
@@ -141,7 +141,8 @@ void *k_mem_pool_malloc(struct k_mem_pool *pool, size_t size)
 	 * get a block large enough to hold an initial (hidden) block
 	 * descriptor, as well as the space the caller requested
 	 */
-	if (size_add_overflow(size, sizeof(struct k_mem_block_id), &size)) {
+	if (size_add_overflow(size, WB_UP(sizeof(struct k_mem_block_id)),
+			      &size)) {
 		return NULL;
 	}
 	if (k_mem_pool_alloc(pool, &block, size, K_NO_WAIT) != 0) {
@@ -152,14 +153,14 @@ void *k_mem_pool_malloc(struct k_mem_pool *pool, size_t size)
 	(void)memcpy(block.data, &block.id, sizeof(struct k_mem_block_id));
 
 	/* return address of the user area part of the block to the caller */
-	return (char *)block.data + sizeof(struct k_mem_block_id);
+	return (char *)block.data + WB_UP(sizeof(struct k_mem_block_id));
 }
 
 void k_free(void *ptr)
 {
 	if (ptr != NULL) {
 		/* point to hidden block descriptor at start of block */
-		ptr = (char *)ptr - sizeof(struct k_mem_block_id);
+		ptr = (char *)ptr - WB_UP(sizeof(struct k_mem_block_id));
 
 		/* return block to the heap memory pool */
 		k_mem_pool_free_id(ptr);
diff --git a/lib/os/mempool.c b/lib/os/mempool.c
index c2f2db720e1..60b20de41ae 100644
--- a/lib/os/mempool.c
+++ b/lib/os/mempool.c
@@ -349,7 +349,7 @@ void *sys_mem_pool_alloc(struct sys_mem_pool *p, size_t size)
 
 	sys_mutex_lock(&p->mutex, K_FOREVER);
 
-	size += sizeof(struct sys_mem_pool_block);
+	size += WB_UP(sizeof(struct sys_mem_pool_block));
 	if (z_sys_mem_pool_block_alloc(&p->base, size, &level, &block,
 				      (void **)&ret)) {
 		ret = NULL;
@@ -360,7 +360,7 @@ void *sys_mem_pool_alloc(struct sys_mem_pool *p, size_t size)
 	blk->level = level;
 	blk->block = block;
 	blk->pool = p;
-	ret += sizeof(*blk);
+	ret += WB_UP(sizeof(struct sys_mem_pool_block));
 out:
 	sys_mutex_unlock(&p->mutex);
 	return ret;
@@ -375,7 +375,8 @@ void sys_mem_pool_free(void *ptr)
 		return;
 	}
 
-	blk = (struct sys_mem_pool_block *)((char *)ptr - sizeof(*blk));
+	ptr = (char *)ptr - WB_UP(sizeof(struct sys_mem_pool_block));
+	blk = (struct sys_mem_pool_block *)ptr;
 	p = blk->pool;
 
 	sys_mutex_lock(&p->mutex, K_FOREVER);
diff --git a/tests/kernel/mem_heap/mheap_api_concept/src/test_mheap_concept.c b/tests/kernel/mem_heap/mheap_api_concept/src/test_mheap_concept.c
index 9f70d84e507..4a331c2d8ee 100644
--- a/tests/kernel/mem_heap/mheap_api_concept/src/test_mheap_concept.c
+++ b/tests/kernel/mem_heap/mheap_api_concept/src/test_mheap_concept.c
@@ -31,12 +31,12 @@ void test_mheap_malloc_align4(void)
 
 	/**
 	 * TESTPOINT: The address of the allocated chunk is guaranteed to be
-	 * aligned on a multiple of 4 bytes.
+	 * aligned on a word boundary (4 or 8 bytes).
 	 */
 	for (int i = 0; i < BLK_NUM_MAX; i++) {
 		block[i] = k_malloc(i);
 		zassert_not_null(block[i], NULL);
-		zassert_false((int)block[i] % 4, NULL);
+		zassert_false((uintptr_t)block[i] % sizeof(void *), NULL);
 	}
 
 	/* test case tear down*/