To reproduce: use the attached project and follow the steps from the gif file Workaround: use a custom autocomplete helper: private void radGridView1_CellEditorInitialized(object sender, GridViewCellEventArgs e) { RadDropDownListEditor editor = e.ActiveEditor as RadDropDownListEditor; if (editor != null) { RadDropDownListEditorElement editorElement = (RadDropDownListEditorElement)editor.EditorElement; editorElement.DropDownStyle = Telerik.WinControls.RadDropDownStyle.DropDown; editorElement.AutoCompleteMode = AutoCompleteMode.SuggestAppend; editorElement.AutoCompleteSuggest = new CustomAutoCompleteSuggestHelper(editorElement); } } public class CustomAutoCompleteSuggestHelper : AutoCompleteSuggestHelper { public CustomAutoCompleteSuggestHelper(RadDropDownListElement owner) : base(owner) { } public override void ApplyFilterToDropDown(string filter) { if (filter.Length > 3) { base.ApplyFilterToDropDown(filter); } } }