The relationship between the parent phase grain size and the B2–B19 martensitic transformation start temperature (M s ) was investigated in a Ti–30Ni–20Cu alloy ribbon fabricated by melt spinning. The average grain size of the ribbons increased from 0.7 to 1.2μm with increasing crystallization temperature from 748 to 823K without significant compositional change and precipitation. M s increased from 308 to 317K with increasing crystallization temperature from 748 to 823K, which was ascribed to the increase in grain size.