Background: In Tunisia, water deficit and heat stress during the end of cycle are more frequent and causes significant yield losses. Selection of short cycle lines could be a good solution to escape the effect of heat and drought during the end of cycle. Furthermore, there is little published information on the effect of the sowing date on yield and its components in lentils. The aim of this study was to investigate the effect of the sowing date on yield and its components of some lentil lines. The best productive and early lines will be selected and therefore proposed for registration in the official catalog of plant varieties. The availability of these varieties to farmers could increase lentil production. Methods: Sixteen genotypes of lentil out of which 14 were advanced lines and 2 were checks varieties were used in this study. The field experiment was conducted during the 2017-2018 cropping season at Kef research station located in a semi-arid zone in north western Tunisia. Genotypes were sown on December 15th, 2017 and February, 7th, 2018. Seventeen agro-morphological parameters were recorded. Result: Based on agro-morphological analysis, lentil lines exhibited considerable genetic variability. Among the tested lines, L3 line seem to be the earliest lines. It showed high yield as well in timely and late sown dates. This line deserves more attention to develop short-cycle and high yielding variety.