He then moved to play with compatriots Jens Martin Knudsen, Sámal Joensen and Jens Erik Rasmussen at Leiftur in the Icelandic league only to return to the Faroe Islands after a disappointing season in which the team relegated. Petersen was Faroese league top goalscorer in the 1994 season. He also had a short spell with Danish sides Holstebro BK and Skive IK. John Petersen is the second most scoring football player in the Faroese league, with 147 goals.
Petersen made his debut for the Faroe Islands in an October 1995 European Championship qualifying match against San Marino, coming on as a substitute for Todi Jónsson.
On the 7th of September 2002, Petersen scored 2 goals within the first 8 minutes in a European Championship qualifying match, to give the Faroe Islands a 2-0 lead against Scotland. Given the chance to extend Faroe Islands lead to 3-0 after half time, alone with the goalie, Petersens attempt went above the post, as the ball hit a trench before impact.
The final score ended 2-2. He has collected 57 caps since, scoring eight goals.
He is also the seventh most capped player for the Faroe Islands national side.
Scores and results list Faroe Islands" goal tally first. Petersen is currently (2011) coach of B36 Tórshavn. He was coach of Skála ÍF for one and a half years in 2007 and 2008.
He was assisting coach for Bachelor of Arts Argir in 2009 and assisting coach for Viborg FF in 2007.
Petersen was assisting coach for Faroe Islands national football team in the period 2006 to 2008. Petersen has played on the national handball team of the Faroe Islands.
He played for the clubs StÍF and Neistin.