Denis Casey was the bank's chief executive officer.
He had pleaded not guilty along with three other former banking executives to agreeing a scheme to mislead the public about the true health of Anglo Irish Bank.
Former Anglo executives John Bowe and Willie McAteer were found guilty.
They will be sentenced on 25 July.
ILP's former finance director Peter Fitzpatrick was found not guilty last Friday.
The trial was the longest in Irish criminal history and the longest jury deliberations ever.
The fraud involved so-called circular transactions.
They were designed to disguise the true state of the Anglo's financial health.
In 2008 Anglo loaned €7.2bn to another financial institution, ILP, which then placed the same sum back with Anglo.
The transactions were accounted for on Anglo's end of year balance sheet as customer deposits.
Deposits are way of assessing the market's and consumer confidence in a bank.
Anglo Irish Bank had to be rescued by the Irish government in 2009.
The bailout cost Irish taxpayers about 30bn euros (£23bn).
A former senior bank official has been found guilty of conspiracy to defraud Irish Life and Permanent (ILP) of 7.2m euros (£5.63m).