Owen Haggerty, from Johnstone in Renfrewshire, was sentenced to three months behind bars last month after reportedly trying to break up a street brawl.
The Daily Record newspaper reported his mother Kirsty Reynolds wrote to the King of Bahrain, Hamad bin Isa Al Khalifa, asking for a royal pardon for her son.
She said she “burst out crying” when she was given the news that the pardon had been granted.
Ms Reynolds told the newspaper: “I can’t stop shaking. It is unbelievable news, it is just such a massive hurdle that we have overcome in the fight to bring Owen home.”
Paisley and Renfrewshire South Labour MP Johanna Baxter said she was “very pleased that he has been granted a royal pardon by the King of Bahrain”.
During the weekly business questions session in Westminster on Thursday, Ms Baxter told the Commons that “no-one” from the UK Government would speak with her about the case, when Mr Haggerty was in prison.
She told MPs: “No-one would engage with me to inform me of his welfare or the current status of his case, and that was because apparently I did not have his explicit consent.
“He was sitting in a jail in Bahrain.
“I had his mother’s consent. She was also a constituent, and yet still nobody would speak to me.”
She asked Commons Leader Lucy Powell: “Can the Leader of the House ensure that the FCDO (Foreign, Commonwealth and Development Office) work with me to arrange his urgent deportation back to this country, and that we avoid further delays in the future to MPs securing access to the information they need to support their constituents?”
Ms Powell replied: “I am pleased that Owen Haggerty has now received that pardon this morning. She raised this matter with me a couple of days ago, which is why I raised it with the Foreign Office, which is why they were in touch with her this morning.”
She added that the “Ministry of Defence and the Foreign Office have been working tirelessly behind the scenes to ensure the pardon”, and vowed to press them to work with Ms Baxter and Mr Haggerty’s family “to make sure he comes back to the UK”.