|Date of birth||31 August 1990|
|Place of birth||Thurso, Scotland|
|Height||1.75 m (5 ft 9 in)|
|* Senior club appearances and goals counted for the domestic league only and correct as of 15:05, 27 June 2014 (UTC).
† Appearances (Goals).
Mackay-Steven began his career with Ross County before moving to English Premier League side Liverpool in 2007. After spending two years at Anfield in the reserve and youth sides, Mackay-Steven was released after an injury plagued season. He trained with Fulham before eventually returning to Scotland.
In January 2011, Mackay-Steven joined Scottish Second Division side Airdrie United. Playing in the remaining months of the 2010–11 season for Airdrie United, Mackay-Steven managed a total of 21 appearances scoring twice, both goals coming in the Scottish Cup.
|“||There is great potential there. Gary is a welcome addition to our squad.||”|
—Peter Houston, BBC Sport, 13 July 2011
In July 2011, Mackay-Steven signed a two-year deal with Scottish Premier League club Dundee United. He made his début as a late substitute in a UEFA Europa League match against Śląsk Wrocław and made his league début three days later, again as a substitute.
In late August, Mackay-Steven scored his first goal for the club (and his first career league goal), netting in the 3–3 draw at St Johnstone. By the end of the 2011/12 season, Mackay-Steven had established a regular starting place in the first team and become a huge fans favourite thanks to his large role in helping turn around United's poor start to the season. Mackay-Steven signed an extended contract with Dundee United in January 2012.
Blackburn scouts were reported to have been watching Mackay Steven on 24 August 2013, in Dundee United's 4–0 victory over St. Johnstone, a game in which he scored. On 12 April 2014, he scored Dundee United's second goal in a 3–1 win against Rangers in the Scottish Cup semi–final at Ibrox.
- "Mackay-Steven fair thrilled to joined SPL side Dundee United". BBC Sport. 15 July 2011. Retrieved 18 July 2011.
- "Official Twitter feed". 15 June 2011. Retrieved 19 July 2011.
- "Liverpool sign up Ross County kid". BBC Sport (BBC). 16 March 2007. Retrieved 18 July 2011.
- "Airdrie bring in former Liverpool youth". Scottish Football League. 11 July 2011. Retrieved 18 July 2011.
- "Winger Gary MacKay-Steven joins Dundee United". BBC Sport. 13 July 2011. Retrieved 18 July 2011.
- "St Johnstone 3 Dundee United 3: Perth men count cost of late madness". The Courier. 29 August 2011. Retrieved 30 August 2011.
- "Dundee United's Gary Mackay-Steven extends contract until 2015". BBC Sport (BBC). 13 January 2012. Retrieved 13 January 2012.
- "Dundee United star Gary Mackay-Steven aims to show Scotland boss Gordon Strachan what he's missing". Daily Record. 26 August 2013. Retrieved 3 September 2013.
- Wilson, Richard (12 April 2014). "Rangers 1-3 Dundee United". BBC Sport. Retrieved 14 April 2014.