He attended Tri-Village High School [3] and began to take part in track and field and cross country running while there.

At the 2014 Mid-American Conference (MAC) indoor meet, Murphy won the mile run and was runner-up over 3000 meters.

In February he ran a personal best and school record of 4:00.39 minutes for the indoor mile run.

[6] On his national debut at the 2015 NCAA Division I Indoor Track and Field Championships he claimed third place in the 800 m with a new best time of 1:47.06 minutes.

In his international debut – also his first time abroad – he surprised by winning the gold medal some four hundredths ahead of Colombia's Rafith Rodríguez, taking the lead in the final stretch.

Murphy finished 12th in 2015 World Championships in Athletics – Men's 800 metres held August 21–25, 2015 in Beijing, China.

His fast finish out-sprinted Boris Berian for the win and Olympic team berth in a personal record 1:44.76.

He won Bronze in the 800m at the 2016 Rio Olympics in a new personal record of 1:42.93, the fifth-fastest time ever by an American.