BACKGROUND Lentil (Lens culinaris Medik.) is an important legume crop cultivated predominantly under dryland conditions where water deficit stress frequently limits yield. Understanding key yield-related and physiological traits that influence grain production under drought is essential for developing effective mitigation strategies. This study aimed to identify these traits and to evaluate the potential of growth regulators and bacterial inoculation to alleviate the effects of water stress in lentils. RESULTS Field studies were conducted as a factorial experiment over two consecutive years using combinations of Pseudomonas fluorescens seed inoculation and foliar application of spermidine (0, 0.5, and 1 mM) and melatonin (0, 50, and 100 mu M). Analysis of variance revealed significant effects for all treatments and their interactions on agronomic traits, yield components, and physiological parameters. Stepwise regression analysis showed that 100-seed weight, number of seeds per plant, and stem dry weight had the greatest direct positive effects on seed yield, whereas leaf dry weight had a negative effect. Among physiological traits, soluble sugars, photosynthetic pigments, and antioxidant enzyme activity were positively associated with yield, whereas total phenols, flavonoids, and malondialdehyde were major negative contributors. The combined application of 100 mu M melatonin and 1 mM spermidine significantly improved sugar accumulation, photosynthetic pigment content, and antioxidant enzyme activity while reducing oxidative damage indicators. CONCLUSION The integration of biochemical and statistical analyses effectively identified key traits driving lentil yield under drought stress. Foliar application of melatonin and spermidine also shows promise as an agronomic practice to improve lentil tolerance and productivity in water-limited environments.