The global asset consultant has won a mandate with an industry super fund managing more than $14 billion.
Mercer has been appointed by CareSuper as the fund's administration partner, taking responsibility of customer and fund support services from next year.
CareSuper chief executive Julie Lander pointed to Mercer's integrated technology capabilities, highlighting the industry fund's reliance on technology support would be satisfied by its new partner.
"This announcement signals an exciting phase in the fund's strategic program and forms part of a larger organisational transformation that will ensure a seamless, quality member experience, as well as new service offerings," she said.
"Whilst both companies provide a similar range of services, it was determined that Mercer's solution will enable the Fund to meet its strategic objectives more quickly."
Mercer Australia managing director and chief executive Ben Walsh said Mercer's investment in people capability, process innovation and technology solutions would allow it to give CareSuper a different kind of partnership.
"We are thrilled to have been selected by CareSuper and our team is excited about the work we will do together," Walsh said.
The appointment follows Link Group's confirmation that its contract with CareSuper would not be renewed. According to an ASX statement released by the administrator on Thursday, the mandate with CareSuper represented about 1% of its pro-forma revenue.