To reproduce: public Form1() { InitializeComponent(); BindingList<Item> items = new BindingList<Item>(); for (int i = 0; i < 30; i++) { if (i % 3 == 0) { items.Add(new Item(i,"Item" + i, IndeterminateBoolean.YesAndNo)); } else if (i % 3 == 1) { items.Add(new Item(i, "Item" + i, IndeterminateBoolean.Yes)); } else { items.Add(new Item(i, "Item" + i, IndeterminateBoolean.No)); } } this.radGridView1.DataSource = items; this.radGridView1.AutoSizeColumnsMode = GridViewAutoSizeColumnsMode.Fill; this.radGridView1.EnableFiltering = true; this.radGridView1.ShowHeaderCellButtons = true; this.radGridView1.ShowFilteringRow = false; } public class Item { public int Id { get; set; } public string Name { get; set; } public IndeterminateBoolean IsActive { get; set; } public Item(int id, string name, IndeterminateBoolean isActive) { this.Id = id; this.Name = name; this.IsActive = isActive; } } public enum IndeterminateBoolean { No, Yes, YesAndNo } Workaround: use custom filtering http://docs.telerik.com/devtools/winforms/gridview/filtering/custom-filtering