In order to study the phenological and morphological characteristics, comparison of yield and yield components, correlation between traits and determination of the parameters affecting seed yield, a field experiment was carried out at the Research Farm of Shahrekord University in 2007. Ten lentil genotypes were compared by a randomized complete block design with three replications. The analysis of variance indicated that there was a significant difference among genotypes for all evaluated traits. Considering significant negative correlation between growing degree days to physiological maturity and seed yield, early maturing genotypes such as genotypes Precoz and L3685, which could grow well before coinciding with high temperature will be produced high yield at Shahrekord climatic condition. Seed weight showed significant negative correlation with number of seeds per plant, number of seeds per pod and number of pods per plant. Since, correlation of number of seeds per plant and number of pods per plant with seed yield were positive, it is expected that the genotypes with lower seed weight could compensate the reduction in their yield by producing either more number of pods or seeds per plant. The results of standard multiple regression analysis between seed yield and its components and also the effects of morphological traits on seed yield showed 100 seeds weight, number of seeds per pod and number of pods per plant highly affected seed yield. Among yield component, 100 seeds weight showed high correlation with seed yield and also showed the maximum positive direct effect on it. Therefore, this component of yield may be considered as the best criteria for indirect selection to increase seed yield. Cluster analysis indicated that the genotypes were different for all studied characteristics and were grouped into high and low yielding genotypes and the high yielding genotypes were early maturing ones.