The Bellinzona-based Federal Criminal Court threw out the public prosecutor's case against Oskar Holenweger, and ordered the state to pay him 395,862 francs in damages and interests as well as 35,000 francs for moral tort.
No reasons were offered in the immediate ruling issued by the court.
Switzerland's federal prosecutor had sought a 30-month prison sentence with a partial suspension against Holenweger.
Prosecutors however failed to convince the court of the private banker's alleged role in Alstom's suspected transfer into secret funds.
Swiss magistrates opened several investigations against the railway network and power grid maker in 2003, mainly over allegations of corruption and money-laundering related to contracts in South America and Asia.
They estimated that between 1995 to 2003 millions in bribes were paid by Alstom through subsidiaries to secure public tenders.
The investigations were carried out in close cooperation with French and Brazilian authorities, officials said. Britain's Serious Fraud Office also searched company premises during a probe last year.
Alstom has repeatedly rejected the accusations.