Educated at Royal College, Colombo, he joined the Ceylon Army and received his basic officer training at the Royal Military Academy, Sandhurst where he was awarded the Overseas officers Cane in 1956 for the Overseas Officer Cadet obtaining the highest place in the Order of Merit of Passing Out.

He was the first Sri Lankan officer to become qualified as an Instructor in Gunnery (IG).

[1] In 1963, he was transferred to the newly formed 4th Field Regiment following the attempted military coup.

He served as the commanding officer of the 4th Field Regiment, Sri Lanka Artillery from February 1981 to January 1982.

Major General Jayaratne was a graduate of the National Defence College, India gaining the ndc qualification.