Cowpea varieties respond differently to plant population per hectare due to their intrinsic morphological differences and the influence of the weather and soil condition in growing environment. The objective of this study was to investigate the effect of plant population on growth and yield characters of erected and semi-erected cowpea varieties in two agroecological zones of Burkina Faso. A split-plot experiment with three replications conducted in two consecutive rainy seasons, 2019 and 2020, at Kamboinse and Farako-Ba research stations was used to determine the effect of three plant population, 62,500 (control), 95,258 and 111,111 on four improved cowpea varieties, KVx745-11P, Komcalle, Tiligre, Neerwaya. The results showed a significant variation of fodder and grain yield in both locations. At Farako-Ba the combined years data recorded the values of 3740.50, 5240.94 and 5164.02 kilogram per hectare for fodder yield and 1124.14, 1242.93 and 1372.93 kilogram per hectare for grain yield at the plant population of 62,500, 95,238 and 111,111, respectively. The same trend was Observed in Kamboinse with slightly higher average means of fodder and grain yield which were 4300.75, 6446.06, 6699.06 kilogram per hectare and 1285.82, 1481.06 and 1650.03 kilogram per hectare, respectively. From the study it is also noticed that grain and fodder yield were impacted by genotypes and environment. The positive relationship between plant population, fodder and grain yield suggest that improved cowpea varieties yield can be substantially increased with the plant population of 111,111 per hectare.