An ultra-fine grain carbide cutting tool material was fabricated by using Sinter-HIP technique. Four-tooth solid carbide end mills with a 20 mm diameter and a 0.8 mm corner-radius were manufactured and then coated with physical vapor deposition multilayer TiAlN and AlCrN coatings. Cutting performance of coated ultra-fine grain carbide end mills was investigated via high-speed wet milling tests on Ti-6Al-4V alloy with a TiAlN coated fine grain end mill commercially available for comparison. The transient and progressive cutting forces during wet machining were measured and the chip morphologies were analyzed. The results of the milling tests revealed that the TiAlN coated ultra-fine grain solid carbide end mill exhibited longer tool life, smaller progressive cutting forces, and better broken chips than the TiAlN coated fine grain end mill with the same cutting condition. In addition, the multilayer TiAlN coated end mill achieved higher tool wear resistance than the multilayer AlCrN coated end mill. The longer tool life of the new coated ultra-fine grain solid carbide end mill should be attributed to the smaller grain size of the tool substrate material with higher hardness, higher transverse rupture strength, and better thermo-mechanical fatigue properties, as well as higher wear resistance of TiAlN coating.