Donnelly dated actress Clare Buckfield for ten years between 1993 and 2003, and television presenter Georgie Thompson from January 2009 until April 2011. On 13 November 2014, Donnelly became engaged to the duo's manager Ali Astall, with whom he had been in a relationship for over a year, with the marriage taking place at St Michael's Roman Catholic Church, Elswick, Tyne and Wear, on 1 August 2015. The ceremony was conducted by his brother, Father Dermott Donnelly, a Catholic priest, with McPartlin as his best man. On 1 September 2018, after announcing earlier in the year that the couple were expecting their first child, Donnelly's wife gave birth to a daughter, whom the couple revealed had been named as Isla Elizabeth Anne.