Hillier was born in Blackheath, London and had played schoolboy football for his region before joining Arsenal in January 1984 as an associated schoolboy. He later became a trainee and turned professional in February 1988; Hillier captained the Arsenal side which beat Doncaster Rovers in the 1988 FA Youth Cup final. He progressed to the club's reserve side, winning the Football Combination in 1989–90, before making his first-team debut in a League Cup tie against Chester City on 25 September 1990. Hillier became a frequent, though not first-choice, player in the Arsenal side that season, making 16 appearances in central midfield, as Arsenal won the First Division title with only a single defeat. The following two seasons Hillier became more of a regular fixture; he played 43 matches in 1992–93, and made a name for himself as a combative, strong midfielder who would make up for any shortcomings in skill with his workrate. However, a leg injury near the end of the season meant he missed both the League Cup and FA Cup finals that season; Arsenal won both, the first time an English club had completed the Cup Double. Hillier returned the next season but another injury forced him to miss the club's 1994 UEFA Cup Winners' Cup Final victory over Parma. By now he was less of a regular in the Arsenal side, especially after the signing of Stefan Schwarz, although Hillier did finally play a cup final for Arsenal, featuring in the Gunners' unsuccessful defence of their Cup Winners Cup title in 1995, losing 2–1 to Real Zaragoza. Despite this, Hillier's form had clearly declined since his early days at the club, and he was a marginal player under Bruce Rioch. Following several off the field incidents by the time Arsène Wenger succeeded Rioch in autumn 1996, Hillier was already on the transfer list and did not feature in Wenger's future plans for the side. Having played 142 matches for Arsenal, Hillier was sold.
Later career
He joined Portsmouth for £250,000 and, despite being sent off on his debut against Oldham Athletic, cemented himself a first team place at Fratton Park. Hillier played 61 matches in two and a half years for Pompey, before moving on again. He joined Second DivisionBristol Rovers in February 1999, where he scored twice against Wycombe Wanderers in the League Cup and Luton Town in the league. However, his spell here was not a success and he was released in 2002; he had a spell at Barnet before retiring in 2003.
Management career
He was appointed manager of non-leagueOldland Abbotonians at the start of the 2008–09 season. before moving to Almondsbury UWE in 2010. He also co-commentates on Arsenal matches for Arsenal TV, does guest appearances/after dinner speeches and attends charity events for Arsenal legends. He also find time to support local football teams in the Bristol area. Hillier has joined up with amateur player Yinka Brownlow and helps provide football coaching in association with UWE to talented youngsters in the Bristol area. He left the club in November 2013.
Controversies
Whilst with Arsenal, Hillier's behaviour off the pitch had started to concern the management. In March 1995, a drugs test at the Arsenal training ground revealed that Hillier had taken cannabis, but he avoided punishment after explaining that traces of the drug had entered his bloodstream due to passive smoking and not a spiked cigarette. A bizarre incident in 1995 at Gatwick Airport, where he was caught stealing £3,000 of another passenger's luggage, further damaged his Arsenal career; he was later fined and ordered to pay costs by magistrates.
Personal life
He subsequently worked as a fireman in the Bristol area.