Mielekamp replaces Bruce Stalder, who only lasted a year in the top job.
In comes at a time of transition for the Mariners, who finished eighth on the ladder this season with just five wins.
Phil Moss was sacked as coach in March, 16 months after succeeding Graham Arnold.
He was replaced by Tony Walmsley, who has since been retained on a full-time basis after initially taking the role in an interim capacity.
Mielekamp has previously worked with NRL clubs South Sydney and Penrith and was most recently the head of commercial business at Western Sydney Wanderers.
"Shaun's record ... will help the Mariners create a sustainable and stable model that will be the backbone of the club for many years," Central Coast Mariners owner Mike Charlesworth said.
"The fact that Shaun has lived locally in the coast for many years and understands the local environment is an added bonus."
Mielekamp will work as one of the club’s executives alongside Kathryn Duncan (Finance Director) and Walmsley, reporting directly to Executive Vice Chairman, Peter Storrie.
"I am delighted that Shaun has joined us, who we identified as the person that the Mariners needed to expand our commercial and sponsorship network," Storrie said.
"Shaun’s appointment has now given us one of the strongest executive teams in the Hyundai A-League, that works as one with our supporters and commercial clients that will give the club sustainability on the coast, along with entertaining, free flowing, attacking football."
