diff --git a/src/inventory/application/services/add_product_service.rs b/src/inventory/application/services/add_product_service.rs
index 2030090..a446bc9 100644
--- a/src/inventory/application/services/add_product_service.rs
+++ b/src/inventory/application/services/add_product_service.rs
@@ -10,7 +10,9 @@ use mockall::*;
 
 use super::errors::*;
 use crate::inventory::{
-    application::port::output::db::{product_id_exists::*, product_name_exists_for_category::*},
+    application::port::output::db::{
+        category_id_exists::*, product_id_exists::*, product_name_exists_for_category::*,
+    },
     domain::{
         add_product_command::AddProductCommand,
         product_added_event::{ProductAddedEvent, ProductAddedEventBuilder},
@@ -29,7 +31,7 @@ pub type AddProductServiceObj = Arc<dyn AddProductUseCase>;
 
 #[derive(Clone, Builder)]
 pub struct AddProductService {
-    // TODO: check if category ID exists
+    db_category_id_exists: CategoryIDExistsDBPortObj,
     db_product_name_exists_for_category: ProductNameExistsForCategoryDBPortObj,
     db_product_id_exists: ProductIDExistsDBPortObj,
     get_uuid: GetUUIDInterfaceObj,
@@ -38,6 +40,14 @@ pub struct AddProductService {
 #[async_trait::async_trait]
 impl AddProductUseCase for AddProductService {
     async fn add_product(&self, cmd: AddProductCommand) -> InventoryResult<ProductAddedEvent> {
+        if !self
+            .db_category_id_exists
+            .category_id_exists(cmd.category_id())
+            .await?
+        {
+            return Err(InventoryError::CategoryIDNotFound);
+        }
+
         let mut product_id = self.get_uuid.get_uuid();
 
         loop {
@@ -138,6 +148,7 @@ pub mod tests {
                 mock_product_name_exists_for_category_db_port_false(IS_CALLED_ONLY_ONCE),
             )
             .db_product_id_exists(mock_product_id_exists_db_port_false(IS_CALLED_ONLY_ONCE))
+            .db_category_id_exists(mock_category_id_exists_db_port_true(IS_CALLED_ONLY_ONCE))
             .get_uuid(mock_get_uuid(IS_CALLED_ONLY_ONCE))
             .build()
             .unwrap();
@@ -162,6 +173,7 @@ pub mod tests {
             .db_product_name_exists_for_category(
                 mock_product_name_exists_for_category_db_port_true(IS_CALLED_ONLY_ONCE),
             )
+            .db_category_id_exists(mock_category_id_exists_db_port_true(IS_CALLED_ONLY_ONCE))
             .get_uuid(mock_get_uuid(IS_CALLED_ONLY_ONCE))
             .db_product_id_exists(mock_product_id_exists_db_port_false(IS_CALLED_ONLY_ONCE))
             .build()
@@ -172,4 +184,24 @@ pub mod tests {
             Err(InventoryError::DuplicateProductName)
         )
     }
+
+    #[actix_rt::test]
+    async fn test_service_category_id_doesnt_exist() {
+        let cmd = get_command();
+
+        let s = AddProductServiceBuilder::default()
+            .db_product_name_exists_for_category(
+                mock_product_name_exists_for_category_db_port_false(IS_NEVER_CALLED),
+            )
+            .db_product_id_exists(mock_product_id_exists_db_port_false(IS_NEVER_CALLED))
+            .db_category_id_exists(mock_category_id_exists_db_port_false(IS_CALLED_ONLY_ONCE))
+            .get_uuid(mock_get_uuid(IS_NEVER_CALLED))
+            .build()
+            .unwrap();
+
+        assert_eq!(
+            s.add_product(cmd.clone()).await,
+            Err(InventoryError::CategoryIDNotFound)
+        )
+    }
 }