He served as the mayor of Bologna from 25 June 2009 until 28 January 2010, when he was forced to resign as he was being investigated for crimes such as embezzlement, fraud and aggravated abuse of office following allegations made by his former lover.

[6][7] On 13 October 2008, Delbono announced his intention to stand in the Democratic Party primary election for mayor of Bologna.

[8] Delbono's candidacy was backed by several prominent figures in Bolognese politics, including: Sergio Cofferati,[8] Romano Prodi,[9] Pier Luigi Bersani,[10] Renato Zangheri[10] and Salvatore Caronna.

[13] On 9 January 2009, Delbono announced that he would be resigning as vice-president of Emilia-Romagna and regional assessor in order to focus on his election campaign.

[17] Delbono was forced to announce his resignation as mayor on 25 January 2010 following the revelation that he was being investigated for crimes such as embezzlement, fraud and aggravated abuse of office.

[19] His resignation was confirmed on 28 January following the approval of an emergency budget, the election to appoint Delbono's successor must take place by 28 March 2010.