Brian became an apprentice at Newcastle United as a teenager and went on to become a member of the Newcastle United FA Youth Cup winning side of 1985, playing alongside Paul Gascoigne, and signed professional forms for the club in 1986.

In the 1987/88 season, he started 30 league games for the Magpies in the left-back position and his performances earned him a call-up to the England Under-21 squad in May 1988 for a tour of Toulon. Unfortunately, Brian was forced to pull out of the squad through injury.

He was sold to Bradford City for £150,000 in 1989, making 145 appearances for the Yorkshire club, and famously scored the last-gasp penalty that pinched a point at Elland Road on Grand National Day 1990 in a heated local derby against Leeds United.

It was while at Bradford that Tinnion expressed himself when pushed forward onto the left side of a three-man midfield in the early 1990s and Tinnion soon established a reputation for having the most creative left foot outide the top division. Tinnion found himself top-goalscorer in all competitions across all four divisions by Christmas 1991 with 13 goals, but he picked up a career-threatening injury at Hartlepool on Boxing Day 1991 in front of a host of top-flight scouts. His injury was surprisingly overcome in time to start the 1992/93 season in Bradford's starting line-up, but before the season was out, in March 1993, he failed to agree a new contract and moved on to Bristol City for a controverisally low tribunal-set fee of around £180,000.

Brian playing at Ashton Gate for Bristol City

His first goal for his new club came against bitter rivals Bristol Rovers with a last-gasp penalty, which immediately endeared him to the fans. Then, most famously, in January 1994 he scored the winning goal in City's giant-killing FA Cup win over Liverpool at Anfield. Brian went on to make over 500 appearances for Bristol City, scoring 36 goals in twelve years at the club.

He went on to become one of City's dominant players of the 1990s and was held in great affection by the Ashton Gate supporters. He switched from wide on the left flank into the centre of midfield under new manager Danny Wilson in 2000 and the role often gave him time and space to execute through balls. Such was his form in that role that he was voted as the best player in his division. He became player-coach in 2000, having helped coach the club's youth teams since the mid-90s, and succeeded Danny Wilson as manager in 2004.

After his departure from Bristol City, Tinnion had spells with Aldershot Town and Team Bath, before retiring as a player in June 2007 to concentrate on developing the Costa Futbol Academy.