Since the liberalization of animal health services in Kenya in the early 1990s, community-based animal health workers (CBAHWs) have become an important alternative animal health delivery channel in the country's marginal areas. However, professional veterinary practitioners have questioned the effectiveness of CBAHW programmes in animal health service delivery in Kenya. This is partly due to lack of information about their performance and partly because CBAHW programmes were implemented before the necessary changes in the existing legal, policy and institutional frameworks had been made. This study was designed to provide such information. In this regard, the productivity of livestock herds among farmers who utilized the services of CBAHWs was compared to that of livestock belonging to farmers who utilized the services of professional veterinarians. The annual live births per mature female (birth ratio) and the proportion of young stock to mature females (breeding index) was computed over a period of 3 years in cattle and goat herds under care of CBAHWs and professional veterinarians. The birth ratios in cattle and goats under CBAHWs were not significantly different from those under the care of professional veterinarians (p > 0.05). Furthermore, the breeding index of cattle and goats under the two categories was not statistically different. Besides the CBAHWs providing clinical services, they also created positive externalities through participatory learning enjoyed by neighbouring livestock keepers, who later dispensed with their services. Policy attention is therefore needed to enhance the participation of CBAHWs in animal health service delivery and to appropriately integrate their activities into the existing formal animal health delivery system in Kenya. Interventions that improve the professional development of these workers, with emphasis on areas pertaining to care of young stock, would not only promote the sustainability of CBAHW programmes but would also improve livestock productivity in the country's marginal areas.