[3] Sims played his junior football for the Gerringong Lions and Wests Panthers before being signed by the Brisbane Broncos, along with his brothers, Ashton and Tariq in 2008.

[5] In 2012, Sims was named at prop in the inaugural Under 20's State of Origin match for Queensland,[6] but withdrew due to a broken hand.

[9] On 3 June, Sims re-signed with the Newcastle side on a two-year contract after rejecting offers from North Queensland and the Manly-Warringah Sea Eagles.

[12] In Round 7 against the Brisbane Broncos, Sims scored his first NRL career try in Newcastle's 32–6 loss at Hunter Stadium.

Fiji lost the test match 32–16, but Korbin stole the limelight with a massive shot on Samoan opponent Isaac Liu.

[17][18] On 10 May, Sims groped the genitals of opposition player and former teammate Willie Mason, an action described by Rugby League writer Brad Walter as being "infantile", "bizarre and offensive", and worthy of punishment due to the potential for the incident to portray the NRL in a distasteful and damaging light.

[31] In Round 25 against the Parramatta Eels, Sims suffered a season ending arm injury in Brisbane's 52–34 loss at Suncorp Stadium, later ruining his chances to play for Fiji in the 2017 Rugby League World Cup.

[36] On 9 September, Sims endured a horror afternoon on the field against his future side St. George Illawarra as his brother Tariq ran past him on three occasions to score a hat-trick in the club's 48–18 defeat in week one of the finals eliminating Brisbane from the competition.

[37] Sims made his debut for St. George Illawarra against his former club the Brisbane Broncos scoring a try in a 25–24 victory at Suncorp Stadium.

[39] On 15 February, Sims suffered a broken arm whilst playing for St. George Illawarra in the pre-season NRL Nines tournament against Parramatta.

[41] In November 2020, Sims signed a two-year deal with the Hull Kingston Rovers in the Super League.

On 29 August, it was announced that Sims would be one of eleven players who were to depart Hull Kingston Rovers at the end of the 2022 season.