Cooney recently came under fire for editing government scientific reports to cast doubt on the link between greenhouse gases and climate change.
Before joining the Bush administration, Cooney worked as a lawyer for the American Petroleum Institute, the oil industry's primary lobbying voice in Washington DC.
He is expected to join the company this autumn.
'We have always hired people for their talent, not their politics,' ExxonMobil spokesman Russ Roberts said. Cooney is expected to partly serve as an 'analyst of sorts', Roberts added.
He said Cooney was offered the job before his role in editing the scientific documents was made public in June.