Whitehead, 24, has turned out for Celtic in a couple of their pre-season games and has done enough to impress manager Simon Haworth and receive a deal.
He played for Southern United in New Zealand last season, and previously spent six seasons with Limerick in Ireland.
Comfortable in midfield or at centre-back, Whitehead had trials at West Ham and Wycombe Wanderers before signing for Limerick in 2011.
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