An inner-Melbourne cafe has been caught ripping off more than 30 workers by nearly $38,000, and will have to issue a written apology and back pay.

Casual employees with Super Max Coffee, trading as Mitte Cafe at Fitzroy North, were underpaid $37,520 in loadings, overtime and penalty rates between July 2017 and June 2018.

The company and its director George Younan has agreed with the Fair Work Ombudsman to back pay the 32 workers and provide them with an apology letter.

He has to display a notice in the cafe and on social media outlining the workplaces breaches and conduct two external audits of pay and conditions this year and in 2020.

Cooks, kitchen attendants and waiting staff were among the staff underpaid, and 12 of the 32 workers were aged under 26.

One was underpaid $3582 after getting hourly weekend rates of $23 despite being entitled to $28.22 and $31.50 on public holidays when they were owed $47.03.