<p>Lentil is a vital grain crop worldwide due to its low production cost, diversifying nature, and nutritional benefits. However, due to its slow growth and weak competitive ability, weeds are the major problem for this crop, reducing its productivity and requiring herbicide use for proper management. Efficient management strategies, including pre-emergence herbicides, are critical to achieving optimal yields. Establishing the critical period for weed control (CPWC) is necessary to develop an integrated weed management plan. This study was conducted at the University of Agriculture, Faisalabad, Pakistan, and comprised two factors (factor A: no pre-emergence herbicide application and pendimethalin as a pre-emergence herbicide; factor B: weed competition and free periods). The logistic and Gompertz non-linear models were utilized to establish the beginning and ending of the CPWC, respectively. A substantial decline in weed biomass of ~ 80.5% and ~ 85.1% was recorded where pendimethalin was applied compared to ~ 73.7 and 68.6% in control across the two growing seasons (2021-22, 2022-23). Also, the average grain production was ~ 1100&#xa0;kg ha^− 1 and ~ 370&#xa0;kg ha^− 1 in treated and untreated plots. The CPWC with pre-emergence herbicide began at 35 DAS and ended at 84 DAS; on the contrary, the CPWC started at 20 DAS and ended at 94 DAS, based on 5% acceptable yield loss. The CPWC is beneficial for devising the proper weed management plan in lentils if a pre-emergence herbicide is used.</p>