David Brock, 73, was last seen at 11.40am on Wednesday 15 May 2024 in the Craddock Way area of the town.
Mr Brock is described as slim built, 5ft 8ins tall, with slicked back long grey hair.
He is believed to be wearing black trousers, black shoes, a dark blue knitted cardigan and a white or grey t-shirt underneath. He also wears glasses.
He is thought to be on foot and often walks around Rainham and Bredhurst.
Anyone with information should call Kent Police on 999 quoting cad 15-0854.
