Echinochloa crus-galli (L.) P. Beauv. is a dominant and competitive weed in the dry-seeded rice system. It imparts negative competition for various resources and may cause a complete yield loss. Therefore, population-dependent E. crus-galli (0–175/m2) with a fixed level of rice density was evaluated to elucidate the influence on the growth and yield of rice plants and E. crus-galli as well. It was revealed that rice plants without E. crus-galli produced 60% more tillers and generated 57% more leaves with increased dimensions. This resulted in accumulating 36% more rice plant biomass than density at 175/m2. Likewise, panicles were  4% longer, contained 40% more grains/panicle, and 37% heavier with fewer un-filled grains/panicle than E. crus-galli of 175/m2. Generally, an increase in the density of E. crus-galli from 25–175/m2 gradually decreased the yield attributes. Among the E. crus-galli densities at 25/m2, E. crus-galli  plants were shorter by 22%, produced 103% more tillers, 36% more leaves, 72% longer, 53% wider and accumulated 56% more plant biomass, with 52% longer inflorescence, 86% more caryopsis/inflorescence, 62% heavier inflorescence over density of 175/m2. However, from the density at 100/m2 onwards, caryopsis/m2 started declining and inflorescence became lighter.