After leaving F.C. United, Johnson joined Dundee United's development squad as an amateur player in March 2015. He signed a three-year professional contract in May 2015 and made his first-team debut as a substitute two days later, in a Scottish Premiership match against Inverness Caledonian Thistle.[2] Dundee United manager Jackie McNamara described Johnson as a "crowd pleaser" with "great potential".[4]
On 1 September 2016, Johnson was loaned to National League club York City, managed by McNamara, for the rest of the 2016–17 season.[5] On 31 January 2017, his loan to York and his Dundee United contract were both cancelled by mutual consent.[6]
On 4 August 2020, Johnson made a return to Scottish football, signing for Premiership club Hamilton Academical.[7] Along with teammate Tunde Owolabi, he was released by mutual consent in February 2021.[8]
Later that month, Johnson signed a contract with Greenock Morton of the Scottish Championship until the end of the 2020–21 season.[9] He made his debut for Morton from the bench in a defeat against Ayr United.[10] He left Morton in June 2021 when his contract expired.[11]