Regis's most significant successes in individual events came when competing in the 200 metres. He was the first British athlete to run under 20 seconds for the distance, and still holds the UK record for the event. He was an indoor world champion and an outdoor World Championship runner-up at the distance, and also finished sixth in the event at the 1992 Olympic Games.
Regis also achieved considerable success running in relay races, winning major international medals in both the 4 x 100 metres relay and the 4 x 400 metres relay. Most notably, he ran the third leg for the British 4 × 400 m relay team at the 1991 World Championships in Tokyo, helping them defeat the heavily-favoured team from the United States and claim the gold medal. He was also a part of the British 4 × 400 m team in 1990 which set a European Championship record for the event. On 3 March 1991, Regis was a member of the British team which set the world indoor record for the rarely contested 4 x 200 metres with a time of 1:22.11, which has not yet been bettered.
Growing up Regis competed for Lewisham at the London Youth Games. John Regis was awarded an MBE for his services to athletics. In 1989, he opened an all-weather running track at Wellesley Recreation Ground (known as "the Well") in Great Yarmouth.
In 1995, Respect, a 30-minute documentary was made about Regis, produced and directed by Pogus Caesar and broadcast on Carlton TV in London. In 1996, John Regis featured on an episode of GamesMaster on channel 4, winning the 'We're athletic, we like lycra' challenge on the Sega Saturn game Athlete Kings. Since his retirement from athletics in 1999, Regis has worked in the media and sports management. In 2012 John Regis was inducted into the Class of 2012 London Youth Games Hall of Fame.
John Regis's 15-year-old nephew, Adam Regis, was stabbed to death on Saturday 17 March 2007 in Plaistow, Newham, east London. The killers were described in media reports as five black youths, who fled in a car. He had been following in his uncle's footsteps as an athlete.