Central Coast have not named a replacement with the existing coaching staff of John Hutchinson, Matthew Nash, Brice Johnson and Ben Cahn to continue preseason preparations while the club search for a permanent replacement.
Walmsley, 50 , spent 16 months in the Mariners top job after replacing Phil Moss in April 2015.
During his tenure on the Central Coast Walmsely's record was five wins, five draws and 25 losses.
The Mariners finished with the wooden spoon in last season’s A-League and were shock losers to Victorian NPL side Green Gully in an FFA Cup round of 32 match last week.
Walmsley said in a Mariners statement that he believes his work will set a platform for the Central Coast to return to the top of the A-League in the near future.
"It's time for me to move on to explore a number of opportunities,” Walmsley said.
"I'm happy with my contribution to the club over a number of years.
"Last year was particularly tough and I sacrificed a lot, but I'm confident the work undertaken will bear fruit.
"I believe in the group of players I've assembled for this season and the new coach will be coming into a much healthier environment than the one I inherited."
Mariners vice-chairman Peter Storrie added: "On behalf of the Central Coast Mariners' board of directors I would like to thank Tony Walmsley for the level of commitment, dedication and passion that he gave to this club.
"Under Tony's tutelage most recently as the club's head coach and originally as head of youth development, many young Australian players have been exposed to the Hyundai A-League.
"Tony has been crucial to the major steps forward this club has taken in regards to fan engagement that was made evident during his continuous availability to initiatives such as; Member functions, pre-game Skype calls and genuine interest in fan/media engagement.
"Tony's reign at the club was through a difficult period of restructuring of the team which he carried out with no complaints like a true professional and got on with the job. We wish him every success in the future."
