Ian Malone and his son Missing, 44-year-old missing from Gateshead.
Ian Malone, 44, did not return home after leaving an address in Rowlands Gill, Gateshead, with his child, who cannot be named for legal reasons.
Northumbria Police said their priority is ensuring both are safe.
Mr Malone is white, about 5ft 5in tall, with mousey-brown hair and was last seen wearing black clothing, a black face mask and carrying a black bag.
Det Ch Insp Jane Fairlamb said: “We need to trace their whereabouts as soon as possible.