Unite Union leader Mike Treen is on his way home after being detained by Israeli forces while taking part in a flotilla delivering aid supplies to Gaza.
He was on board a fishing boat which was part of the flotilla trying to break the 11-year Israeli blockade of the Palestinian territory.
Mr Treen said he was tasered repeatedly and suffered injuries to his face and head as armed and masked Israeli soldiers forced their way onto the boat.
Unite Union national secretary Gerard Hehir said Mr Treen flew out of Tel Aviv earlier today on a plane to Hong Kong and from there would travel to Auckand.
He said Mr Treen was expected back in New Zealand around lunchtime tomorrow, but there could be complications as the Israeli authorities refused to return his passport.
The Israeli Embassy in New Zealand said the flotilla to Gaza was in direct violation of international law and a cynical publicity stunt. It said by imposing the legal naval blockade, Israel was "exercising its right to self-defence by aiming to prevent the illegal smuggling of arms to Hamas, a world-recognized terror organisation."
Green Party co-leader Marama Davidson was detained in 2016 when part of a similar flotilla was intercepted by the Israeli Defence Forces.