After impressing in a youth tournament, Hoilett signed for English club Blackburn Rovers at the age of 13, and was loaned to SC Paderborn and FC St. Pauli in the German 2.

Hoilett spent four years at the Loftus Road club – alternately in the Premier League and Championship – before moving to Cardiff on the expiration of his contract.

[9][10] He travelled the world with his club and gained attention at a tournament in Wales; he turned down an extended trial with Manchester United to join Blackburn Rovers as he believed he had more chance of breaking into the first team at the latter.

In order to qualify for one in future, Blackburn looked to loan Hoilett to a club in another European country, with the player rejecting possible moves to Belgium and France.

[21] In the summer of 2009, Hoilett was granted a work permit on appeal, allowing him to continue his fledgling career in England at the Premier League level with Blackburn.

[23] After impressing during the club's pre-season schedule, Hoilett made his debut for Blackburn in the opening day of the 2009–10 season as a late substitute in place of El Hadji Diouf during a 2–0 defeat to Manchester City.

[24] He was named in the starting line-up for the team's following match and scored his first competitive goal for Rovers in a 3–1 League Cup win over Gillingham on 25 August 2009.

[25] His performances in the early stages of the campaign prompted the club to open talks over a contract extension as Hoilett was in the final year of his original deal.

Coming on as a second half substitution, he won a stoppage time penalty which Benni McCarthy converted to put Rovers 3–2 up, before Paulo Ferreira equalised in the 122nd minute.

[30] Hoilett made his first Premier League appearance of the 2010–11 season on 21 August 2010, coming on for Nikola Kalinić in the 84th minute in a 2–1 defeat at St Andrew's against Birmingham City.

[32] Hoilett scored his first league goal on 23 January 2011, in a 2–0 home victory against West Bromwich Albion at Ewood Park, converting in the 47th minute from a Nikola Kalinić assist.

On 12 February 2011, he made his fortieth Premier League appearance for Blackburn when he featured against Newcastle United in a goalless draw, and was replaced at half-time due to a slight hamstring strain by Morten Gamst Pedersen.

On 9 April 2011, Hoilett scored in the 1–1 draw against Birmingham City before half time, but was unfortunately injured in the 68th minute, being replaced by Australian Brett Emerton.

Hoilett scored his fifth league goal of the campaign with an individual effort, coming in a 3–2 win against Wolverhampton Wanderers at Molineux Stadium on the last day of the season.

[35] After refusing a contract renewal with Blackburn Rovers, Hoilett joined Queens Park Rangers on 27 July 2012, for a fee decided by tribunal.

[50] He scored his first Premier League goal since 2012 in a 2–1 comeback win over Wolverhampton Wanderers on 30 November, which BBC Sport called a "fabulous first-time effort from 25 yards".

[citation needed] His last appearance for the club came on 27 January against Barnsley in the first game in charge for new manager Mick McCarthy, but he didn't feature at all the rest of the season.

[60] On 16 February 2024, Junior signed for Scottish Premiership club Aberdeen on a short term deal until the end of the 2023–24 season, reuniting with manager Neil Warnock.

[34] In February 2011, he rejected a call-up from the Canada national team, stating that he wanted more time to develop his club career before committing to international football.

[69] He received his first international cap in a 1–1 draw against Ghana on 13 October 2015, at RFK Stadium in Washington, D.C.[70] He officially got cap-tied to Canada after starting for the nation in a 2018 World Cup qualification match against Honduras.

Hoilett was named to Canada's squad for the 2017 CONCACAF Gold Cup on 27 June 2017,[71] and scored his first international goal in the quarter-finals on 20 July, in a 1–2 defeat to eventual finalists Jamaica.

[74][75] Hoilett was named Canada's captain for the first time in a CONCACAF Nations League match against Cuba on 7 September 2019; he scored three goals in a 6–0 victory.

[84] In June 2024, Hoilett was initially named to Canada's squad for the 2024 Copa América,[85] but was forced to withdraw following a lower-body injury in training camp and was replaced by Joel Waterman.