"Alex has worked long hours and travelled thousands of kilometres to raise awareness and encourage loyalty to the Zone amongst our clubs, rugby league players and supporters.
"We will be sorry to lose him, but appreciate that after so many years in the game, Alex wants to take a break and spend some time with his family.
"He leaves a wonderful legacy and we have no doubt our new general manager will have a solid foundation to build on."
Since arriving in Northland, Smits drove a rise in participation numbers, increased the Northern Zone's public profile, was committed to the rugby league pathway and worked tirelessly to improve the game experience locally.
Smits said highlights of his time in Northland included seeing the NZ Kiwis play Toa Samoa at Toll Stadium during last year's Four Nations, the creation of the RLN Premiership Finals series into an event on the Northland sporting calendar and the growth of league in the Northland primary and secondary schools.
He also introduced the Leadership through League programme and led the push to improve sideline behaviour with the Don't Be an Egg campaign.
Rugby League Northland is also losing the services of club development officer Toni Haldane.
"Toni is well known in the rugby league community for her commitment and empathy in supporting clubs and the game," Wells said.
"She has built a great rapport with the clubs during her time with Rugby League Northland and is well respected amongst her peers. We wish both Toni and Alex the very best."
Smits and Haldene will remain in their roles until December 18.