Ajay Singh Yadav was born on 2 November 1958 in a Yadav family at Saharanwas village, Rewari district, Haryana. His father was Rao Abhey Singh, who had also been a Member of the Legislative Assembly in Haryana. He was educated at various places including Jaipur, Chandigarh, New Delhi and Rewari, graduating with the degrees of BSc and LL.B. Singh became second lieutenant in the Indian Army on 7 June 1980, and resigned seven years later on 26 June 1987 as captain.