ASB is reviewing the ownership of its Aegis investment and custody business, which administers $15.2 billion of funds.
The bank says a strategic review will assess whether Aegis's potential could be better realised under new ownership.
The review, which is expected to take six months, continues a trend among Australian banks to sell assets – including financial advice and wealth management units – in the wake of the Australian Royal Banking Commission.
ASB tried to sell Aegis in 2010 but advanced talks with Pyne Gould Corp's then subsidiary Perpetual Group broke down.
In February this year ASB chief executive Vittoria Shortt told the Herald the bank was reviewing its operations following the Royal Commission report which was scathing of behaviour by institutions, including the bank's parent, the Commonwealth Bank.