The Home Office reversed a previous decision to deny Arnel Cabrera, 38, residency in the country after his wife Mayra died in 2004.
Ms Cabrera was given the wrong anaesthetic and died at Great Western Hospital in Swindon.
A theatre nurse at the hospital, Ms Cabrera was a Unison member and the union has been fighting ever since to allow Mr Cabrera to stay in the country.
Unison general secretary Dave Prentis said: 'I am delighted that the Home Office has seen sense and reversed its decision.
'Unison funded Arnel’s fight to remain in the UK as we firmly believed he and his son Zac had the right to build the family life they had planned before Mayra’s tragic death.’