After beginning his career with Willesden Hawkeye in the early 1990s, he joined Isthmian League Premier Division side Stevenage Borough in February 1994, and impressed with the club in his first two seasons there.

Hayles was signed by Plymouth Argyle by new manager Ian Holloway for a fee of £100,000 prior to the 2006–07 season, where he quickly established himself as a supporters' favourite after a hugely impressive start which earned him the nickname "The Ox in the box".

[7] On 31 December 2007, Hayles joined Leicester City on an emergency loan, which became permanent for a fee of £150,000 on 2 January,[7] signing an 18-month contract.

[12] Following his loan spells with Cheltenham Town, Hayles had a brief run in the Leicester first team upon his return, but failed to score a single goal.

[20] He scored his first goal for the club on 9 October 2010 in a 6–0 win against Halesowen Town as City went joint top of the Premier Division table.

[23] "Barry has settled in fantastically well and has been a great boost for the squad and the club," said Lee Hodges, the manager of Truro City and a teammate of the striker during his time at Plymouth Argyle.

[26] On 24 July 2013, Hayles signed for Arlesey Town after he had scored twice in the first half of their 6–0 friendly win over Langford the previous evening.

Chesham United manager Andy Lees stated, "He has a lot to offer on the pitch still and now off it as well as he looks to start a coaching career".

[29] In Chesham United's 1–0 win at Bristol Rovers in the FA Cup on 8 November 2015, Hayles came on as a substitute, receiving an ovation from both sets of supporters.

[34][35] Following Merstham's relegation from the Isthmian League Premier Division in 2022, Hayles, along with manager Frank Wilson, departed the club.

Hayles was called up to the Cayman Islands squad in 2000 for a pair of FIFA World Cup qualifying matches against Cuba.

He took part in an unofficial 5–0 friendly defeat to American club side D.C. United, but he never played for them in a full international after FIFA ruled that he did not meet eligibility requirements.