Canadian left-sided player Jim Brennan joined the Canaries on a three year deal on July 1st 2003. Brennan turned down an offer of a new contract from Nottingham Forest for whom he made 47 appearances in 2002/03. Out of contract with Forest after spending four years at the City Ground, he was free to join the Canaries for no fee. Prior to joining Forest, Jim played for Bristol City making 55 appearances in a career that started during the 1996/97 season. He had trialled with Celtic before joining the Robins

Brennan operated primarly as a left-back for Forest but is expected to play on the left side of midfield for City and Nigel Worthington was keen to see him in partnership with last season's player of the season Adam Drury. "I wrote Drury and Brennan down on a bit of paper and it looks very good, very solid,” said the City boss.“We've got Adam who is defensively very sound and then there's Jim who has got terrific pace and strength and is very good going forward. The two combined should hopefully make us very strong on that side... Myself and Doug Livermore have tracked him for quite a few games and he's very quick, very, very good at going forward and, while he can play at left-back, he's better going forward and will add something to our team. He's a big loss for Forest, but a big gain for us."

Brennan added: “Forest made me an offer but I spoke to Nigel and he made it sound so good as he talked about his ambition to take the club into the Premiership. I had a great four years at the Forest but this a great opportunity for me to achieve my ambition, which is the same as the manager's. However it was initially thought that this would be placed on hold as Jim was selected to jet out to the USA on July 12th to join up with the Canadian squad for the CONCACAF Gold Cup. However Jim opted to remain with the Canaries and earn his place in the first team.

Injuries delayed Brennan's debut for the Canaries until the winter months. After a smattering of appearances as substitute, he made his full debut in the FA Cup Third Round clash at Everton on January 3rd 2004 and scored Norwich's only goal in a 3-1 defeat.

On 27th January 2006, Jim switched to Southampton on a free transfer, bahing only 6months remaining on hiscontract and not figuring in the Canaries' first team plans although he had made 21 appearances during the first half of 2005/6. He had struggled with injury and loss of form at Carrow Road. His contract with the Saints will last initially until the end of the 2005/6 season.

Released by the Saints, Jim joined Major League Soccer side LA Galaxy on trial in June/July 2006. On September 8th, 2006, it was announced that Brennan will be heading to Toronto to join the city's new MLS team Toronto FC for the 2007 season, becoming the first player in the club's history

Jim made 84 appearances for Toronto and was the club captain for the 2007 and 2008 seasons

Jim retired from playing in the spring of 2010 and was appointed Assistant General Manager at Toronto on 6th April 2010.

In March 2015, he became executive director at Aurora Youth Soccer Club. As well as youth and women’s teams, they field Aurora FC in the semi-professional League One Ontario. League One Ontario is one of two top level Canadian leagues although Canadian teams do play at higher levels with their American counterparts in the Major League Soccer (MLS), North American Soccer League (NASL) and the United Soccer League (USL).

n 2018, Brennan joined Carlo Baldassarra and Preben Ganzhorn to found York Sports and Entertainment; the company will own the upcoming Canadian Premier League club York 9 FC. On 27th July 2018, York 9 FC announced executive vice president of soccer operations Brennan as the club's first head coach. York 9 FC were inaugural members of the Canadian Premier League that commenced on April 27 2019 (with York 9 drawing 1-1 with Forge FC). They rebranded as York United FC

On 23rd November 2021 York United announced that they had parted company with Brennan.

Jim played 49 times for Canada and scored 6 international goals.