His first game will be against the Wellington Firebirds in Nelson, on November 19.
Jayawardene retired from national duties in March but he recently plied his trade in the Caribbean (Jamaica Tallawahs) and English T20 (Sussex) leagues.
While the Stags clinched the Ford Trophy one-day domestic cricket bragging rights last summer, Malan says they are seeking consistency in all three formats.
"We want to finish on the top half of all three competitions," he says, adding that winning one and finishing in the bottom half of the other two is a "good" season but not a "successful" one.
"If we can be on top half of all competitions and adding the players we've produced in the past couple of months playing for the Blacks Caps, then we're moving in the right direction."
Will Young needs consistency, especially after scoring 900-odd runs in the red-ball format last summer.
"Building on that and trying to push for 1000 runs this summer is one of his goals and he showcases his white-ball skills to show how good a player he is," he says, adding Jesse Ryder "offers both sides of the coin" as an all-rounder.