Since independence Kenya has adopted several reforms and policies in health sector. One of the aims of these policies and reforms is improving efficiency, resource allocation and use. The new Kenyan constitution has extensively devolved health care services provision to the counties with the goal of achieving efficiency and proper use of resources. This study estimates technical efficiency and factors that influences it among public health centres in Kakamega County for the years 2013 and 2014. We used number of outpatient visits, number of children fully immunized, number of family planning visits and number of at least four antenatal care visits as output variables and medical personnel and number of beds/cots as input variables. Our sample comprised of thirty six public health centres. Data envelopment analysis (DEA) was used in estimating efficiency scores. The efficiency scores were then regressed against selected variables to determine their effects on efficiency. Various diagnostic tests were performed before estimation. From the results the average variable return to scale technical efficiency is 87% with the least efficient health centre score of 15.3% and the most efficient health centre score of 100%. Antenatal care visits influenced efficiency positively while medical personnel and beds/cots influenced efficiency negatively. The study recommends redistribution of medical personnel as well as extra beds/cots to other health facilities in the county based on assessed needs.