A combination of the two methods of stability analysis, the additive main effect and multiplicative interaction (AMMI) and the best linear unbiased prediction (BLUP), based on weighted average of stability (WAASB) estimated by the linear mixed models (LMM) index identified the improved genotypes. In this study, 17 advanced genotypes of lentil were studied at two locations, Zanjan and Maragheh, during the two seasons. To examine the genotype × environment interaction, the AMMI and BLUP methods using the WAASB and weighted average of mean performance (WAASBY) index were combined to evaluate the performance stability of genotypes according to different experimental plots. Considering the significant genotype × environment interaction based on likelihood ratio test (LRT), data were analyzed by the BLUP method. The highest grain yield was detected for genotype 13, followed by genotypes 7, 11, 20, 5, 12, and 19 with higher productivity than the grand mean. To select genotypes according to yield and stability, the WAASBY index was defined by combining mean grain yield and stability. Considering 50:50 contributions for the two components, the grain yield and stability of the 13 genotypes were higher than the grand mean. The highest WAASBY was observed for genotypes 7, 20, and 12, which were determined as the best genotypes of lentil under agroecological conditions encountered in the current study regions.