Cochinchin gourd (Gac) (Momordica cochinchinensis Spreng) oil cake was studied to use as an ingredient in diet for rainbow trout (Oncorhynchus mykiss). The chemical composition of gac oil cake used in this study was 11.2 percent protein and 13.1 percent lipid. Four experiment diets in which Gac oil cake was incorporated at 5 percent, 10 percent, 15 percent and 20 percent were fed to rainbow trout from 600 g/fish to 1 kg/fish. Imported Finland feed .was used to compare with four above experiment diets. Results showed no significant difference in voluntary feed intake, growth performance and feed conversion ratio of rainbow trout fed diets contents of 5 percent, 10 percent and 15 percent cochinchin gourd (Gac) oil cake. Increase the cochinchin gourd (Gac) oil cake incorporation to 20 percent occured the significant decrease of growth performance, voluntary feed intake and feed conversion ratio of rainbow trout. Imported Finland feed showed the highest growth performance and lowest feed conversion ratio (FCR 1.05). The pink color of rainbow meat of fish fed 15 percent and 20 percent cochinchin gourd (Gac) oil cake diets was similar to that of fish fed Finland diet. The results indicate that cochinchin gourd (Gac) oil cake can be incuded 15 percent in diet for rainbow trout as coloring ingredient. Fish fed 15 percent cochinchin gourd (Gac) oil cake diet showed the average daily weight ADG of 2.78 g/fish/day and FCR of 1.25.