Dack, who took over in the summer, will step aside at the Enclosed Ground following Monday’s 4-0 defeat to Havant and Waterlooville.
The heavy loss came after the Hawks secured their first point of the season on Saturday at home to Braintree.
First team player Dan Harding will now take control of first team affairs while they look for a replacement.
A club statement moments ago confirmed the changes. It read: “The club would like to thank Jimmy for his efforts and wish him the best of luck in the future.
“Dan Harding steps up as Whitehawk’s new caretaker manager following the resignation of Jimmy Dack last night.
"Dan began his career at Brighton & Hove Albion and also played for Leeds United, Ipswich Town, Southend United, Reading, Southampton, Nottingham Forest and Millwall before joining the Hawks in September 2016. Harding is also a former England U21 Player.”
Whitehawk’s next match is at home to Poole Town on Saturday.