Police are asking for anyone who has seen the missing man not to approach him.
38-year-old Brett Iverson who is thought to be in the Cheltenham area.
He was reported as missing from the Abergavenny area last Friday.
He is described as being 6ft 3ins tall, of a large build with short, shaved hair. He was last known to be wearing grey Adidas tracksuit bottoms, a black Puma t-shirt with a white logo, grey and orange Under Armour trainers and a quilted jacket.
Anyone who has seen Brett is urged to contact police immediately and not to approach him as he may be unpredictable.
Anyone who has information on where he may be, or anyone who has seen him, is urged to call police on 101 and quote incident 307 of 21 September. If seen at the time of calling dial 999.