Innovation in agricultural sector is inevitable. One of the key agricultural sub-sector in Kenya that innovations plays a critical role is poultry production. The indigenous poultry production in the country is still very low compared to the very high demand for indigenous poultry products. The low productivity per indigenous poultry farmer is largely attributed to diffusion of innovation to cope with the challenges of the common free-range method. In this study, using information from 326 farmers in Kitui County, the study examined the relative effect of co-operative membership compared with the effects of other socio-economic factors on farmers’ adoption of poultry farming innovations. Co-operatives has a high effect compared to other socio-economic factors such as age, sex, and level of formal education. Thus, for adoption of agricultural innovation, a co-operative is a platform for innovators, early adopters and early majority. It therefore recommended that intervention programs in the agricultural sector should focus more attention on developing, strengthening and expanding farmers’ co-operatives for better diffusion and use of innovations; and better linking of the social capital with extension service agencies, funders, markets, and other agricultural value chain players.