The East African Journal of Social Sciences and Humanities 1920: Vol 1(2)Engaging in off-farm employment among farming households may either have a competing effect or complementary effect with households’ own farm work. Both effects have implications on the household's ability to enhance farm investment and reduce poverty. This study first examines the role of off-farm employment on financing farm inputs, and secondly, it assesses the effects of labour devoted to off-farm employment on a household’s farm labour supply. The survey data from 309 randomly selected farming households in five villages of the Kilombero Valley were used. Tobit model that considers cornered solution has been used. Results from the econometric estimation show that holding other factors constant, the increase of non-farm self-employment income is associated with more expenditure on inputs. Qualitative evidence, however, suggests that some forms of labour-demanding off-farm employment such as those related to farm wage have an undesirable labour effect on labour supply on households’ farms, with repercussions onfarm productivity. It is recommended that rural development policies should establish synergy between farm and off-farm activities taking into account the effect of both income and labour on off-farm employment.