O’Brien, 23, scored for the Tigers as a trialist against Frickley Athletic on Saturday and has been rewarded with a deal for the new season.
He played nine times for Alfreton Town last season.
Previously, he had spells at Aston Villa and Wigan, playing at Wrexham and Chester on loan, before a spell in Finland.
A former England Under 17 international, he had initially agreed to join National League North side Curzon Ashton earlier this summer.
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