South Wales Police say a 33-year-old man from Port Talbot has been arrested on suspicion of murder.
It follows the discovery of a 48-year-old man's body at Villa Terrace in Treboeth, Swansea, at around 6.50pm yesterday evening.
The family and HM Coroner have been informed but no formal identification has yet been made. A post-mortem examination is due to be carried later today.
An incident room has been set up at Cockett police station.
Officers are appealing to anyone with information to contact the incident room on 01792 562732 or Crimestoppers anonymously on 0800 555 111.