The conventional agricultural extension service in Tanzania is mainly provided by extension officers visiting farmers to provide agricultural advisory service. This system of extension service provision faces a number of challenges including the few number of extension officers and limited resources. This article assesses the effectiveness of an impact-driven, radio-based extension service delivery system that has been introduced in some rural areas of Tanzania. The system aims to enable extension officers to reach many farmers with minimum efforts. However little is known about the effectiveness of this new extension service delivery system. Structured questionnaire, focus group discussion, interviews and participant observation were used to collect data from 55 small holder farmers who had been receiving an impact-driven, radio-based extension services through Farmer Voice Radio project. Additional data were collected from interviewing extension officers and from archives of participating community radio stations. The results indicate that in some rural areas, farmers have started sharing agricultural information and best practices. Some farmers have also started to change their farming practices. This brings a new finding that farmers can adopt and practice easily what is aired by their fellow farmers in the community radio stations.