He primarily plays as a, but he can also play in the.
Senior rugby union career
Heidelberger RK (2009-10)
2009-10
Keinhorst began playing rugby union as an amateur with Otley and he later moved to Germany to play for Heidelberger RK in 2009, at the age of 19, and he won the National Championship in the 2009-10 season. He played eight games and scored four tries in his first season.
Otley (2010-11)
2010-11
Keinhorst rejoined Otley as a semi-professional in 2010, and went onto make 11 appearances in the 2010-11 season, scoring three tries before leaving at the end of the season to sign a professional contract at rugby league side the Leeds Rhinos.
Senior rugby league career
Leeds Rhinos (2012-18)
2012
Keinhorst signed for the Leeds Rhinos in 2011, and made his Super League début on 30 July 2012, in the defeat by the Wakefield Trinity Wildcats. Keinhorst came on as a substitute in the Leeds Rhinos' losing effort in the 2012 Challenge Cup Final defeat by the Warrington Wolves at Wembley Stadium.
Keinhorst scored a hat-trick of tries for the Leeds Rhinos in round 2 of the 2018 Super League season, against Hull Kingston Rovers at Elland Road. It was revealed at the end of the 2018 campaign, that Keinhorst would be departing the Leeds Rhinos to sign a contract to play for Hull Kingston Rovers.
Hull Kingston Rovers (2019 - present)
2019
In October 2018, Keinhorst signed a three-year deal with Hull Kingston Rovers. On 9 January 2019, Keinhorst received the number 4 jersey ahead of the start of the Super League season. On 13 January 2019, Keinhorst made his non-competitive Hull Kingston Rovers' début in a pre-season friendly against the Widnes Vikings, Keinhorst claimed a 30-16 victory with his new club. Keinhorst made his first competitive appearance for Hull Kingston Rovers in round 1 of the 2019 Super League season, Keinhorst scored a dramatic try in the final six seconds of the match on his début, going onto record a thrilling 18-16 victory over cross-city rivals Hull F.C. at Craven Park.
Representative career
Rugby union
He made his début for Germany in a match against Poland on 20 November 2010. Keinhorst scored his first try for Germany a week later against the Netherlands in Amsterdam.
Rugby league
Keinhorst is the youngest of four rugby-playing brothers and qualifies to play for Germany through his German father Wolfgang, who has lived in the United Kingdom for many years. Jimmy and his three brothers, Kristian, Markus and Nicholas set a world record in 2007, when they played in a rugby league international game for Germany against the Czech Republic, becoming the most siblings to play in a rugby league international match. As of 2012, Keinhorst was the top try and point scorer for Germany.
