diff --git a/internal/modules/string/commands.go b/internal/modules/string/commands.go
index c71254d..1ab2550 100644
--- a/internal/modules/string/commands.go
+++ b/internal/modules/string/commands.go
@@ -168,7 +168,30 @@ func handleSubStr(params internal.HandlerFuncParams) ([]byte, error) {
 }
 
 func handleAppend(params internal.HandlerFuncParams) ([]byte, error) {
-	return []byte("Hello World"), nil
+	keys, err := appendKeyFunc(params.Command)
+	if err != nil {
+		return nil, err
+	}
+
+	key := keys.WriteKeys[0]
+	keyExists := params.KeysExist(keys.WriteKeys)[key]
+	value := params.Command[2]
+	if !keyExists {
+		if err = params.SetValues(params.Context, map[string]interface{}{
+			key: internal.AdaptType(value),
+		}); err != nil {
+			return nil, err
+		}
+		return []byte(fmt.Sprintf("$%d\r\n%s\r\n", len(value), value)), nil
+	}
+	currentValue := params.GetValues(params.Context, []string{key})[key]
+	newValue := fmt.Sprintf("%v%s", currentValue, value)
+	if err = params.SetValues(params.Context, map[string]interface{}{
+		key: internal.AdaptType(newValue),
+	}); err != nil {
+		return nil, err
+	}
+	return []byte(fmt.Sprintf("$%d\r\n%s\r\n", len(newValue), newValue)), nil
 }
 
 func Commands() []internal.Command {
@@ -210,5 +233,14 @@ Overwrites part of a string value with another by offset. Creates the key if it
 			KeyExtractionFunc: subStrKeyFunc,
 			HandlerFunc:       handleSubStr,
 		},
+		{
+			Command:           "append",
+			Module:            constants.StringModule,
+			Categories:        []string{constants.StringCategory, constants.ReadCategory, constants.SlowCategory},
+			Description:       `(APPEND key value) If key already exists and is a string, this command appends the value at the end of the string. If key does not exist it is created and set as an empty string, so APPEND will be similar to [SET] in this special case.`,
+			Sync:              true,
+			KeyExtractionFunc: appendKeyFunc,
+			HandlerFunc:       handleAppend,
+		},
 	}
 }
diff --git a/internal/modules/string/key_funcs.go b/internal/modules/string/key_funcs.go
index 1eff2b6..792f6bc 100644
--- a/internal/modules/string/key_funcs.go
+++ b/internal/modules/string/key_funcs.go
@@ -55,12 +55,12 @@ func subStrKeyFunc(cmd []string) (internal.KeyExtractionFuncResult, error) {
 }
 
 func appendKeyFunc(cmd []string) (internal.KeyExtractionFuncResult, error) {
-	if len(cmd) != 4 {
+	if len(cmd) != 3 {
 		return internal.KeyExtractionFuncResult{}, errors.New(constants.WrongArgsResponse)
 	}
 	return internal.KeyExtractionFuncResult{
 		Channels:  make([]string, 0),
-		ReadKeys:  cmd[1:2],
-		WriteKeys: make([]string, 0),
+		ReadKeys:  make([]string, 0),
+		WriteKeys: cmd[1:2],
 	}, nil
 }