The PSNI said the boy was last seen at 3.40am in the Ballyoran area.
A PSNI spokesperson said: “Police and family are becoming increasingly concerned about the whereabouts of 13 year old Reuben Kerr.
“Last seen at around 0340 this morning in the Ballyoran Area of Portadown. Approx 5ft5, slim build with dark brown hair. Was last seen wearing a black Adidas tracksuit and trainers.
“If you have any information please contact Police on 101 and quote serial number 164 of 29/06/22”