With GESB's financial advice service recently closed, Mr Heffernan's appointment will help provide members in need of tailored financial advice.
"GESB has a number of specialised, untaxed funds which require expert knowledge of their intricacies and complexities for members," said Mercer's head of financial advice Jo-Anne Boch.
"We expect this [appointment] to provide great comfort and confidence to GESB members when they turn to professionals to help them with their superannuation, retirement and financial advice needs."
Mr Heffernan is a former Mercer employee, who left the company six years ago to establish GESB's financial advice business.
He aims to use his more than 35 years of experience in financial services to protect Australian workers heading toward retirement.
"This is the ideal time to form a financial plan for the next phase of their lives to ensure they have income for life," Mr Heffernan said.
"In my experience too many workers do not understand their entitlements and often miss opportunities to maximise their savings."
