Chalcides mertensi is an Algero-Tunisian endemic three-toed skink. It inhabits perennial meadows in north-western Tunisia. The main characteristics of its reproduction traits were studied in six populations, by counting the total number of embryos in pregnant females in relation to their snout-vent lengths (SVLs) and measuring the lengths of newborn individuals. The species is viviparous, with SVLs of gravid females ranging between 103.2 and 220.3 mm, making this species one of the largest among its congeners. The maximal number of embryos per gravid female was 28, ranging between zero and 15 in each of the right and left oviducts. Selection apparently favoured larger females to maximize the number of embryos since a correlation between the number of embryos and female SVL was found. Births occurred during the first week of July, one month earlier than dates given for three-toed Chalcides species in Europe. The species produced one clutch each year.