Production and marketing of African Leafy Vegetables (ALVs) has increasingly become important in areas surrounding Nairobi. This is mainly due to Nairobians' realization of their nutritional value. ALVs are particularly rich in mineral nutrients and vitamins that are useful in the management of ailments including HIV/AIDS. In addition, these vegetables remain extremely important for overcoming food insecurity and alleviating poverty among the rural and urban populations as they are relatively affordable. Alongside these private uses, ALVs also have a public value which includes maintenance of traditions and culture, and contribution to sustainable development, specifically in the conservation of biodiversity alongside other ecosystem benefits. Despite this importance, little economic analysis has been conducted to assess how on-farm conservation of ALV biodiversity (intra and interspecific) in areas around Nairobi is affected by market development. It is against this background that this paper addresses the following research questions: 1) which varieties are demanded by the market in Nairobi and for what reasons, and 2) what is the effect of market development on on-farm biodiversity of ALVs around Nairobi? To address these research questions, the study uses empirical data derived using both qualitative and quantitative methods. An econometric model was specified to estimate effect of market development and other determinants of ALV biodiversity levels. Results indicate consumers demand only certain ALVs due to the nutritive aspects associated with them. However, the effect of market development on on-farm diversity of intra and inter-specific ALVs species is mixed. While market development in terms of gross sales has no significant effect, spatial dimension of market development reduces intra-diversity of ALVs. The paper concludes by deriving policy implications on conservation of ALVs on farms surrounding Nairobi and its peri-urban areas.