Nicholas Briggs, 28, went missing from HMP Leyhill in South Gloucestershire last Thursday.
He is serving an 18-month sentence for domestic assault and was arrested by Gwent Police on Sunday night.
A second inmate, Anthony McCormick, 52, who absconded at the same time, and who was handed a life sentence in 1998 after being convicted of rape, handed himself into police on Friday.
A second inmate who absconded from an open prison has been arrested.