The Lake Egirdir is the fourth largest lake in Anatolia, with an area of 468 km2. By using a mark-recapture method, the population of Emys orbicularis was monitored for three consecutive years (2011-2013) and data regarding their population size, sex ratio and information about habitats used was gathered. During the whole sampling period, 4 juveniles, 105 males and 98 females were captured and marked. According to the POPAN model, the three-year super -population size of Lake Egirdir was calculated as 460 individuals. Capture rate and survival rate was calculated as 0.17 and 0.61, respectively. Sex ratio was determined nearly equal (males : females = 1.07). The Lake Egirdir population is the only one showing increasing trend among the Mediterranean populations of E. orbicularis in Turkey.