Many inactive materials have been found to be helpful for improving the electrochemical performance of Co electrode in alkaline rechargeable batteries, including B, P, Si, S, Si3N4, and BN. In this paper we find for the first time that selenium has a similar effect with them. Selenium incorporation is realized through a liquid-reduction method. The obtained Co–Se sample is investigated as the negative electrode material of alkaline rechargeable battery. Experimental results demonstrate that the Co–Se sample electrode shows excellent electrochemical reversibility and considerably high charge–discharge capacity, showing a great potential to enhance the electrochemical performance of Co-based alkaline rechargeable batteries. The electrochemical reaction mechanism and function mechanism of Se are also investigated.