Understanding the reproductive dynamics of a fish species is a fundamental aspect to provide sound scientific advice for fisheries management. So, the aim of this study is to afford some aspects of the reproductive dynamics of Tilapia zillii for the first time in a Ramsar site (Ayata Lake), south-eastern Algeria. A total of 470 individuals of T. zillii (224 males, 231 females, and 15 undetermined) ranging in size from 3.53 to 23.8 cm TL, were sampled in a Ramsar site (Ayata lake) between November 2018 and November 2019. The overall sex ratio was 0.97:1 males to females which were not significantly different from 1:1. Seasonal sex distribution was in favor of females during autumn, winter, and spring. Macroscopic examination of gonads and monthly follow-up of gonado-somatic index indicated that spawning occurred once a year between March and August with peak activity in June. The length at first maturity (L_m50) was estimated at 9.7 cm for females and 8.5 cm for males. The condition factor k indicated a good condition of the individuals that is reflected by an accumulation of reserves.