One of the key links in the system of knowledge and information transfer in Serbian agriculture is the extension service, which acts as a mediator between scientific institutions and different user groups.Extension officers prefer to cooperate with already formed user groups, such as agricultural cooperatives, because they unite farmers with similar production and are convenient for group methods of extension work. This paper aims to examine the quality of cooperation between agricultural extension services and agricultural cooperatives in Serbia and to evaluate the views of farmers (cooperative members) on the success of this cooperation. For this research, a survey was conducted with 220 respondents, members of agricultural cooperatives. The analysis showed that over 80% of cooperative members cooperated with extension service, and that they were more satisfied with the quantity of extension services than with the quality.More than half of the respondents believe that extension services need to be adapted to the needs of cooperatives, and that the cooperatives should be given more attention in the media appearances of extension officers. This research provides an important insight into the form and specifics of cooperation between agricultural extension services and agricultural cooperatives, on the basis of which measures for their continuous improvementcan be proposed.