With Barrow he scored a club record 351 tries and kicked 20 goals in exactly 500 appearances from 1943–57. He scored 50 tries in his final season, 1956–57, another club record. He retired after Barrow's Rugby League Challenge Cup final defeat by Leeds in 1957, one of three Wembley appearances he made with the Cumbrian club during that decade.
Lewthwaite's Testimonial match at Barrow took place in 1956.
On the international front he travelled to Australasia with Great Britain in 1946 – the famous "Indomitables" tour, named after the vessel on which they sailed, HMS Indomitable. He top-scored with 25 tries on that tour despite not making the Test team. He also won one England cap.
Jimmy Lewthwaite represented Cumberland.
Challenge Cup final appearances
Jimmy Lewthwaite played Right-Wing, i.e. number 2, in Barrow's 0-10 defeat to Wigan in the 1950–51 Challenge Cup final at Wembley Stadium on Saturday 5 May 1951, and played in Barrow's 21-12 victory over Workington Town in the 1954–55 Challenge Cup final at Wembley Stadium on Saturday 30 April 1955.
Jimmy Lewthwaite holds Barrow's "Most Career Appearances" record with 500 appearances, and is one of the fewer than twenty Welshmen to have scored more than 200-tries in their rugby league career. and is first in Barrow's all time try scorers list with 354-tries.
He was a natural athlete and represented Cumberland at rugby union and soccer as a schoolboy, as well as winning a medal in the All-England Schools Athletics competition at the age of 13. He moved to Woodley, near Reading, shortly before turning 15 to work at an aircraft factory but later relocated to Barrow to take up an apprenticeship at the town's shipyard. He continued to excel as a footballer and had trials with Blackburn Rovers and Preston North End before switching to rugby league with Barrow in 1943, making his first-team debut against St Helens in April that year. He also managed to play golf around the district, after he slowed down from rugby.
- "Jim Lewthwaite - Rugby league record-breaker". independent.co.uk. 2010-12-31. Retrieved 2011-01-01.
- "1950-1951 Challenge Cup Final". wigan.rlfans.com. 31 December 2011. Retrieved 1 January 2012.
- "Barrow at greyhoundderby.com". greyhoundderby.com. 31 December 2011. Retrieved 1 January 2012.
- Robert Gate (1988). "Gone North — Volume 2". R. E. Gate. ISBN 0—9511190—3—6
- "Barrows all time leading try scorers". barrowrlfc.com. 2011-12-31. Retrieved 2012-01-01.