The collective participation of local communities in the management and utilization of forest resources is now widely accepted as a possible solution to the failure of centralized, top-down approaches to forest conservation. Under such initiatives, communities in Kenya have organized themselves into Community Forest Associations (CFAs). Despite the proliferation of CFAs, forest conservation outcomes have been mixed. Little is known about the factors that influence the success of collective action in forest conservation. Using data from 518 households and 22 CFAs within the Mau forest conservancy, this study employed regression techniques to analyze factors that influence household participation in CFA activities. Further, the study investigated the determinants of successful collective action, as measured by the percentage of forest cover and the number of reported cases of vandalism of forest resources. The relationship between household participation and success of collective action was also established. Collective action is more successful where household participation is high, the associations are initiated by the communities themselves, the associations interact frequently with government departments, and the forest cover is low, among other factors. The factors that influence the level of household participation are also identified.