Rob Flannagan is to step down as managing director of Tower following the completion of the listed insurer's strategic review and sale of its health and investment units.
Flannagan will work out the 12 months of his notice, the company said in a statement. He has led Tower for seven years.
"Tower now has a refreshed board with a clear direction of where it wishes Tower to be in the future," he said. "It is time to step aside to allow a new leader to guide the company in its preferred direction."
Tower embarked on a review of what were then its four operating units in 2010 on the basis that its share price didn't reflect the value of the underlying businesses.
Fisher Funds acquired Tower Investments for $79 million last month to add to its KiwiSaver pool in a deal backed by new shareholder TSB Bank.
It sold its medical insurance unit to Australia's nib in November for $102 million and plans to return $120 million to shareholders.
Tower shares rose 0.5 percent to $1.88 and have declined 3 percent this year. It is rated 'hold' based on the consensus in a Reuters survey of four analysts, with a median price target of $2.