This investigation was carried out at Agronomy Department Farm, Faculty of Agriculture, Assiut University, Egypt, to study the effect of temperature resulting from different sowing dates, genotypes and their interaction on forage yield and its components of alfalfa. A set of ten genotypes (Ismailia-1, Nubaria-1, Ramah-1, populations from F.R.S., Kharja, El-Dahlia, Farafra, Balady and Aswan and Cuf 101) were sown on five sowing dates (three at autumn, October 10 th (D1), November 10 th (D2), December 10 th (D3), beside two at spring i.e. March 20 th (D4), April 20 th (D5). Two experiments were carried out as experiment I (2017-2019) and experiment II (2018II ( -2020. Each experiment included all autumn and spring sowing dates. The split block design with three replications was used in both experiments. Fifteen cuts were taken in the two years from each sowing date for each experiment. The results showed that the sowing dates and genotypes had highly significant effect on plant height, leaves/stem ratio, total fresh, dry and protein forage yields for the two experiments, except total protein forage yield in experiment I among studied genotypes which was non-significant. While, the interaction between sowing dates x genotypes insignificant for all studied traits in the two experiments. The highest mean values of plant height obtained from the plants sown in fourth (March D4) and fifth sowing dates (April D5) sowing date were in the two experiments. While, sowing at November (D2) and December (D3) gave the highest mean values of leaves/stems ratio.Furthermore, the maximum total fresh, dry, protein forage yields were obtained from sowing at March 20 th (D4) in experiment I and from sowing on October 10 th (D1) in experiment II. It is remarkable results that the Ramah-1 genotype produced the highest total fresh, dry, and protein forage yields in the two experiments.Finally, the correlations between forage yield and its components revealed that total protein forage yield was positive and significant correlated with fresh and dry forage yield, but negatively correlated with leaves/stems ratio in two experiments.