Under the arrangement, JP Morgan will take on the role as custodian of investments in NSWTG's Financial Management Common Fund and the Trustee Common Fund. BlackRock Investment Management will act as fund manager.
NSWTG chief executive Imelda Dodds said the decision to appoint both companies followed a review of NSWTG's existing funds management and custodian arrangements.
"The review was undertaken to ensure that best practice service standards, investment practices and efficient pricing could be achieved for NSWTG and the clients we represent," Dodds said.
"NSWTG is seeking to harmonise the funds management and custodian arrangements for each of its Common Funds, which will help to facilitate operational efficiencies and improved outcomes for our clients".
NSWTG was founded in July 2009 following the merger of the two parent organisations the Office of the Protective Commissioner (OPC) and Public Guardian and the Public Trustee NSW (PTNSW).
An NSWTG spokesperson said prior to the merger, OPC and PTNSW had separate investment management arrangements.
Previous holders for OPC were State Street Global Advisors, while NSW Treasury Corp acted for PTNSW with BNP as its custodian, the spokesperson said.
Both parent organisations acted as trustee for client funds and operated a Common Fund on behalf of clients, NSWTG said in a statement.