In 2008 Joe had a great first season in the Super League for Castleford scoring 12 tries in 25 games.[5] He was tipped for being a future England RL international.[6]
Hull F.C.
Westerman was Hull F.C.'s marquee signing for Super League XVI, with the Black and Whites paying a club record fee to secure the services of the former Castleford Tigers man.[7]
Warrington Wolves
In October 2015, Westerman signed a 3-year contract with Warrington for a fee of £150,000.[8]
Upon promotion from League 1 in 2017, Westerman signed with Rugby League's first trans-Atlantic team, the Toronto Wolfpack, on 1 October 2017.[12] Westerman joined fellow Wolves teammate Ashton Sims for the 2018 season, who signed with the Wolfpack less than a month prior.[13]
In April 2018 Westerman was released by Toronto Wolfpack after making only 4 appearances for the club. The decision to allow Westerman to leave for free raised eyebrows given he was less than 6 months into a three-year contract and the Wolfpack had paid a transfer fee of £130,000 to secure his services.[14]
Return to Hull F.C.
Westerman returned to Hull FC in April 2018 despite interest from other clubs. He cited coach Lee Radford and his love for Hull FC as reasons for his choice.[15]
In the local derby in June 2019 against Hull Kingston Rovers, he dislocated his knee in a tackle only to slap it back in place and continue playing.[16]
In June 2021, it was announced that Westerman would return to his boyhood club, the Castleford Tigers, on a two-year deal from the 2022 season.[18] He would be working alongside former coach Lee Radford once again, as well as playing for the team he supported as a child. Commenting on the news, he said, "The standard is really high now and I just want to get there and play well for my hometown club next year."[18]
Westerman made his second Castleford debut on 11 February 2022 against the Salford Red Devils.[19] He was voted the Fans' Man of the Match for the first two rounds of the season against Salford and Warrington.[20][21] Following another two Man of the Match performances against Wigan and Leeds in March, head coach Radford called Westerman "the best 13 in the competition".[22] His standout personal year saw him dominate the club's end-of-season awards, being named Directors' Player of the Year, Players' Player of the Year, and Club Player of the Year.[23]
In the 2023 season, Westerman made 23 appearances for Castleford and scored one try against the Leigh Leopards.[2] He served as acting captain towards the end of the season due to the injury absence of Paul McShane.[24] He was named as Players' Player of the Year and Club Player of the Year, retaining the awards for the second consecutive year.[25] In September, Westerman signed a two-year contract extension with the Tigers and said, "I always wanted to end my career at Cas."[26][27] Director of rugby Danny Wilson said, "As a person, he's Castleford through and through. He wears his heart on his sleeve when he plays and he's been our best player for the last 2 years."[28]
In February 2023, Castleford Tigers fined Westerman after an online video was released showing him performing a sex act in public on a woman, who was not his wife. The club also ordered Westerman to help educate young people on the effects of alcohol and "dangers of social media when in the public eye". Westerman issued a statement, saying "I'd also like to apologise to the supporters, sponsors, staff, and directors of Castleford Tigers as well as my team-mates. I'd like to extend this apology to the game of rugby league, and I have realised that I need to work on my decision-making around alcohol."[37][38][39]