Farm diversification is a common coping strategy among smallholder farmers, especially in the developing countries. As a result, understanding the determinants of farm diversity is paramount. Access to extension has been found to be an important determinant of farm diversity through the technology adoption pathway. Despite farmers access to several extension services, no evidence exists on the effect of different extension services on farm diversity. This study evaluates the effect of extension services on farm diversity in Kenya. It uses a truncated Poisson model on a sample of 743 households who were selected using a multi stage sampling technique. The findings show that there are significant differences between the least and the most diversified farms. Furthermore, access to government, private and NGO extension services, alongside farmer demographic characteristics, increases farm diversity. This study therefore recommends for hiring, training and facilitating extension officers. In addition, the different extension services should be used as compliments and targeted to where their impact is highest. Acknowledgement : This research was financially supported by the German Federal Ministry of Food and Agriculture (BMEL) based on the decision of the Parliament of the Federal Republic of Germany (grant number 2813FSNu01).