Abstract: A study to investigate the effect of sowing bruichid-damaged bean seeds on germination, plant development and grain yield was conducted at Sokoine University of Agriculture, Morogoro, Tanzania during the year 2000 cropping season. Unperforated and bruchids damaged seeds with one to four holes were planted in plastic pots and placed in the glasshouse. Germination, plant development and subsequent grain yield were compared using a randomized complete block design. Results indicate that planting bruchid-damaged seeds significantly reduced germination and plant development, negatively impacted bean yield components, increased fungal disease (powdery mildew) severity and reduced seed quality.