A Pakistani court said on Wednesday there is no evidence Asif Ali Zardari killed the chairman of Pakistan Steel Mills, Sajjad Hussein.
The prosecution charged that Zardari plotted the murder of Hussein from his Karachi prison in September 1998.
But Judge Ibrar Hussain Memon concluded the prosecution had not substantiated their allegations.
The acquittal brings the number of standing charges against the ailing ex-senator to five criminal and seven corruption.
Zardari, who served as investment minister in his wife's cabinet, has been in jail since 1996 on what originally amounted to eight corruption and six criminal charges.
Benazir Bhutto has been in exile
In the worst blow against the former first family to date, a Swiss judge last month found Bhutto, Zardari and their Swiss intermediary guilty of laundering $12 million in illegal commissions.
They were given a six-month suspended jail sentence and ordered to return the total funds plus a diamond necklace partly purchased with the funds to Pakistan.
Zardari has only one standing conviction against him in Pakistan, after he was found guilty by an anti-corruption court last year of receiving bribes for a contract between a private group and Pakistan Steel Mills
His wife, Benazir Bhutto, has been sentenced in absentia for corruption in Pakistan, and has been living in self-imposed exile in Britain and the United Arab Emirates since 1999.