Police are appealing for sightings of Joshua Harley and his two children who are travelling in the South Island.
He has not been in contact with his family for four days, prompting them to raise concerns with police.
He was travelling with his children, aged 9 and 12, in a 1996 Nissan Safari with the vehicle registration ELP735.
They were last in Murchison on May 2 and could be in the greater Murchison area or elsewhere in the South Island.
"There are no immediate concerns for either of the group's safety, but police
are keen to locate them to provide reassurance to his family," a statement from Tasman police said.
Anyone with any information on their whereabouts are asked to contact their local police station.