It could be argued that commercially oriented famers pay more attention on reaping short term commercial benefits from their home-gardens and hence would not focus on longer term benefits that could be derived through enhanced biodiversity. Although empirical studies have been conducted to measure trade-offs between commercial orientation and plant diversity, hardly any research has carried out with the focus on homegardens in Sri Lanka. The main objective of this study is to explore the trade-offs between commercial orientation of farmers and plant diversity in homegardens in three districts in Sri Lanka, viz, Batticaloa Kandy and Kurunegala. The specific objectives are to (i) measure the degree of plant diversity in home gardens, (ii) measure the degree of commercial orientation of farmers, and (iii) to econometrically estimate the relationship between plant diversity and commercial orientation of farmers. Data for this study were collected through a survey carried out in the three districts in 2009. Plant diversity was measured using three indices, namely Richness index, Shannon index and Simpson index and the degree of commercial orientation of farmers was measured using a number of proxies to capture the extent of market transactions and perceptions among farmers towards the purpose of farming. A set of multiple regression models were specified treating the levelof commercialization, land size, employment status, education, household income and the geographical region as independent variables and plant diversity as the dependent variable. The results of the calculated indices revealed that homegardens in Kandy and Kurunegala districts are quitediverse in plants and it is not that diverse in Batticaloa district. Approximately one half of the famers in Kandy and Kurunegala districts and four fifth of the farmers in Batticaloa are commercially oriented. The regression results showed that the farmers with commercial orientation tend to maintain home gardens with relatively higher plant diversity in Kandy district. However, commercial oriented farmers in Kurunegala district tend to maintain homegardens with less plant diversity compare to that of noncommercial oriented. The results also revealed that the plant diversity increases with the increase in land extent and 0.42 ha and 0.53 ha was estimated to be the land area which brings about the maximum plant richness in homegardens in Kandy and Kurunegala districts respectively.