Simon Moutter has resigned is leaving country's biggest telecommunications company after seven years as managing director.
He will leave at the end of June and will be replaced by the head of Spark's digital business, Jolie Hodson.
Spark chair Justine Smyth said Ms Hodson was "an accomplished leader with a strong record of delivering results and managing complex business units".
Ms Hodson joined Spark in 2013 and previously been chief financial officer.
Mr Moutter rejoined the company in 2012 and steered Spark through its separation from the network arm of the former Telecom, which became Chorus.
He also also oversaw a restructuring of the company with a new name - Spark - hundreds of job losses, but which also devolved responsibility for decision making to individual business units.
Spark has also moved from a traditional telecommunications company, with a move into sports broadcasting to rival Sky TV.
Ms Smyth said it had always been expected that Mr Moutter would likely stay five to seven years in the top job, and the board had moved early to identify and assess potential internal candidates.
"In almost every respect, Spark today is a vastly different company to the one that Simon re-joined in 2012. We are New Zealand's leader in wireless communications, with a
rejuvenated mobile business across both Spark and Skinny brands, a promising Internet of Things (IoT) business and a determination to be at the forefront of 5G," she said.
Mr Moutter said he had put everything into turning around the company after the demerger and a period of soft performance.
"I feel it's the right time to pass the leadership baton on ... I haven't made any decisions about what I'll do after I finish at Spark, other than committing the first couple of
months to spending some quality time with my family."