The 25-year-old helped the Valiants secure automatic promotion to League One, scoring once in 18 appearances, but he was released at the end of his short-term deal.
He has now returned to League Two with Barrow, who finished 16th last season.
“It’s amazing to finally get it done," Harper said after signing. "I spoke to the gaffer (Andy Whing) recently and our ambitions aligned, and I’m happy to finally be here at this football club.
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“It’s a fearless club who wants to climb the ladder and the table, and I want to be at a club with a winning environment and at a team who have ambitions to do big things, so that stood out to me.”
Harper signed for Ipswich back in 2021 for an initial fee believed to be £500k, rising to £1m if all clauses were met, penning a three-year deal.
He featured just 19 times for the Blues, going out on loan to Crewe Alexandra and Exeter City before being released by mutual consent in June 2023.