The purpose of this study was to determine the effect of Farmer Field School (FFS) approach on adoption of biological control by rice farmers. The research population consisted of 72 farmers who had participated in FFS and 346 who had not participated in FFS, selected through randomized sampling method. The methodological approach of the study was twofold: descriptive-correlative and causal-comparative. Validity of the instrument was established by a panel of experts comrised of senior faculty members in agricultural extension and education department, and of research committee advisors. Reliability analysis was conducted by using Cronbach's Alpha formula the result being 82%. The results indicated that 63.9 percent of the farmers who had participated in FFS adopted the techniques to a large and a very large extent, while only 13.3 percent of those who had no participation in FFS adopted the techniques (to a large, but not very large extent). The results of the multiple regression analysis (stepwise method) revealed that the variables of knowledge of biological control, relative advantage, level of mechanization, rice farming experience, social participation, the number of contacts with extension agent, the extent to which farmers used mass media and information sources described a variation of 75.9% of the adoption of biological control by rice farmers, (farmers who had participated in FFS). Also the results of the multiple regression analysis (stepwise method) revealed that the variable of knowledge of biological control described a variation of 83.1% of the adoption of biological control by rice farmers who had not participated in FFS.