Garvan was a member of the Crystal Palace side that earned promotion to the Premier League in 2013 following a 1–0 win over Watford in the play-off final.

When his contract expired after five years with Palace where he had amassed 87 appearances and 11 goals, he joined League One club Colchester United in August 2015.

[5] Following his success with the youth team, Garvan was handed his professional debut on 6 August 2005, starting in Ipswich's season opening 1–0 win over Cardiff City at Portman Road.

[8] In the 2006–07 season, Garvan received the first professional red card of his career after being sent off for a second bookable offence during a 2–0 home defeat by Leicester City on 10 February 2007.

[2] After being subject to a £150,000 bid from Ipswich's Championship rivals Crystal Palace in July 2010,[15] Garvan signed for the club for an undisclosed fee on 3 August 2010.

[24] Immediately following Palace's play-off success, he and teammate Peter Ramage signed new two-year deals to remain with the club until 2015.

[25] On 18 August 2013, Garvan made his first Premier League appearance when he started in Palace's 1–0 home defeat by Tottenham Hotspur, playing 66 minutes before being replaced.

[28] After falling of favour with manager Ian Holloway at Crystal Palace, Garvan failed to make an appearance for the first team for the remainder of the 2013–14 season.

[34] After being released at the end of his Crystal Palace contract, Garvan spent the summer of 2015 training with a number of teams, including his former employer Ipswich Town, Southend United and Motherwell in search of a new club.

[36] Just one month after signing his short-term deal with the Essex side, on 25 September, Garvan agreed a contract extension that would keep him with the U's until the summer of 2017.

[42] He made his first appearance of the season on 22 November, providing an assist for Tom Eastman's goal in Colchester's 3–0 win at Cheltenham Town.

[44] After amassing 53 appearances, Garvan left Colchester by mutual consent on 11 April 2017 as his contract was cancelled citing personal reasons.

[45] On 2 July 2017, it was announced that Garvan had returned home to his native Dublin, signing for Premier Division club St Patrick's Athletic, alongside Killian Brennan.

[47] Four days later, Garvan made his league debut for St Pats in a 1–0 defeat to Cork City, but was sent off after an incident in the tunnel at half time.

Garvan's grandfather Con Martin was also an Irish international footballer who had the notable distinction of having been capped in every position for the team, including as goalkeeper.