Gallacher started his career with
Rangers. He helped the Rangers
under-19 team win league and
Scottish Youth Cup doubles in the 2006–07 and 2007–08 seasons being part of the most successful youth team of rangers history. He also travelled with the first team squad for a
UEFA Cup tie against Hapoel Tel Aviv in February 2007 and involved in champions league squads against Stuttgart and Sevilla . He was included in the first team squad on many occasions and was an unused substitute many times, including an
Old Firm derby on 5 May 2007. He joined
Cowdenbeath, then in the
Scottish Third Division on 1 September 2008. In 2010, Gallacher signed a six-month loan deal with
Forfar Athletic which was later extended until the end of the season. Gallacher made his debut for
Rangers in a 4–0 win over
Albion Rovers. In September 2013, Gallacher signed on loan for
Airdrieonians. In July 2014, Gallacher signed for
Scottish Championship side
Heart of Midlothian on a two-year deal. Gallacher made his first team debut on 10 August 2014, coming on as a 67th-minute substitute at
Ibrox Stadium in a league match against
Rangers, replacing the injured
Neil Alexander in a 2–1 win. On 10 September 2015, Gallacher moved on loan to
Forfar Athletic for a second time, joining on a short-term deal. On 14 January 2016, Gallacher signed a contract with
Alloa until the end of the season, after leaving
Hearts by mutual consent. Gallagher signed a one-year deal with
St Mirren in June 2016, beginning the season as the Saints first-choice goalkeeper. After
Jack Ross his former Alloa manager was appointed manager of st mirren in October 2016, Gallacher was surprisingly dropped after man of the match performances in previous two games in favour of
Jamie Langfield, however, he returned to the starting line-up in mid-November, playing in St Mirren's 2–1 victory over
Ayr United in the
Scottish Challenge Cup. Gallacher continued in goal for the side until January 2017. Hibs came calling for Gallachers signature after a mutual agreement to leave st mirren was confirmed.
Hibernian. He left Hibs at the end of his short-term contract, in May 2017, and joined
Dumbarton on 23 June 2017. After 51 appearances for the Sons and an irn bru cup final he rejected a new contract and joined
Scottish League One side
Airdrieonians on a two-year contract in May 2018. Gallacher suffered a serious knee injury in 2018 and was ruled out for a year. He regained his position after the long absence and kept numerous clean sheets until the season was cut short due to COVID-19. On 30 July 2020, Gallacher signed for
Arbroath. In May 2021 Gallacher signed for
East Fife. On 13 January 2023, Gallacher rejoined
Alloa Athletic in league one after some financial difficulties at east Fife. ==Career statistics==