Born and brought up in Ropar in Punjab, Gurtej took interest in football in the sixth grade, thanks to his father. A fan of Jagatjit Cotton & Textile Football Club, Gurtej's father took him to the stadiums. Singh would attend matches of JCT and enjoyed watching Baichung Bhutia and I.M. Vijayan play. Representing his school, Gurtej played at the Challenge Cup tournament in Sector 42 of Chandigarh, aged 15. At the tournament were kids from Football Academy, Mahilpur, a renowned centre of learning which has produced several well-known players. At the end of one the matches in the competition, Gurtej was approached by coach Hassan Ali for trials in what was to be the start of his professional football career.
Career
Early career
Born in Punjab, Singh started his professional career with JCT FC of the I-League where he scored one goal for the club on 15 May 2011 in a league match against Chirag United in which he found the net in the 59th minute to give JCT their equalizer and a final 2–2 draw. After spending the season with JCT's first team, after the club disbanded at the end of the 2010–11 season, Singh signed with the Pailan Arrows.
After spending one season with Pailan Arrows, Singh signed for former I-League champions, Churchill Brothers. He then made his debut for the club on 17 November 2012 in a league match against East Bengal at the Fatorda Stadium in which he came on in the 81st minute for Tomba Singh as Churchill Brothers lost the match 0–3. Singh then made his international club debut on 1 May 2013 in the AFC Cup against Semen Padang in which he came on in the 49th minute for Steven Dias as Churchill Brothers lost the match 1–3.
On 23 July 2017, Singh was picked up by FC Pune City for 2017-18 ISL season. Singh made his debut for Pune City in their opening fixture against Delhi Dynamos, which Pune lost 2-3. Singh was a first team regular at FC Pune City. Playing in the centre-back position, Singh was vital in the defensive unit of Pune, making 109 clearances in the 18 matches played. His first goal for Pune City came on January 24, 2018 during their home fixture against Jamshedpur FC. Singh's equaliser from a corner in the 62nd minute helped Pune win the match 2-1. Pune made it to the semi-finals, their best performance since the inception of the tournament, where they were knocked out by Bengaluru FC.
