Abstract Thynnichthys thynnoides is a type of freshwater fish that commonly inhabit the Teluk Petai Lake and Tanjung Kudu Lake, Kampar Regency. This study aims to understand the reproductive biology of T. thynnoides and has been conducted from December 2020- January 2021. The fish was sampled 4 times, twice/month. Parameters measured were sexual characteristics, sex ratio, gonad maturity l…