ABSTRACT Despite existence of multiple agricultural advisory service providers, there is limited evidence on their contribution to farmers’ productivity. This study applied the multinomial endogenous switching regression model to analyze incremental effects of multiple advisory service providers on the partial and total factor productivities of 665 farmers in Tanzania. The study contributes to the literature by using number of service providers rather than binary or frequency measures of extension access. Results showed that farmers working with two service providers had higher improvement in the productivity of maize as well as all crops grown than those using one, three or four service providers. We recommend targeting of agricultural advisory services to meet specific needs of different crops grown by farmers in various localities, enhanced coordination and monitoring of service providers to enhance the relevance, quality and timeliness of the services provided by different actors so as to improve farm productivity levels.