Abstract: Estimation of the maximum sustainable yield (MSY) is very important in fish stock assessment and management, but the MSY can not often be estimated from the incomplete catch data of commercial fisheries. The MSY was calculated on the data of yellowfin tuna (Thunnus albacares) fishery in the Indian Ocean by the yearly relative rate of catch increment (RRCI) proposed by Grainger and Garcia and compared with the results obtained from the other methods. The MSY for yellowfin tuna fishery was found to be 33.75 × 10^4 t when yearly RRCI equals zero, 3% lower than the MSY estimated through Pella and Tomlinson model. Our results supported the fact that a rough MSY can be obtained by this method as a useful supplementary tool to conventional stock assessment models by calculating RRCI.