Following North Harbour's national provincial championship match against Counties Manukau tomorrow, McAlister will join French club Toulouse.
North Harbour Rugby chief executive Brett Hollister said McAlister had requested an early release due to his new French commitments.
"We've worked with the New Zealand Rugby Union to negotiate an appropriate release with Luke, including an early release fee," Hollister said.
"We're obviously very disappointed that he is leaving during our 2011 ITM Cup campaign - as our season was planned on the expectation Luke would play for us.
"The reality is he wishes to start his new contract in Toulouse this month, and for us that means finishing the season without him," Hollister said.
NZRU General Manager Professional Rugby Neil Sorensen described the move as a "disappointing end" to McAlister's career in New Zealand.
"We have agreed that this is the best outcome for everyone involved and we wish him well," Sorensen said.
