Recalled after a groin strain ruled him out of the recent series triumph in India, Williamson will resume on 77 not out for the final session alongside Daryl Mitchell, who was unbeaten on 16 at the break.
England skipper Ben Stokes won the toss and elected to bowl on a Hagley Oval wicket with a green tinge, but New Zealand denied him the inroads into their batting order he would have liked.
He did get an almost immediate return when Gus Atkinson dismissed Devon Conway caught and bowled for two, and Brydon Carse also struck before lunch to halt a dangerous-looking innings from New Zealand captain Tom Latham at 47.
Williamson and Rachin Ravindra put on 68 for the third wicket before Stokes brought on young spinner Shoaib Bashir, who separated them with a full toss.
Ravindra took on the delivery but only managed to punch it straight to Zak Crawley at midwicket, the all-rounder shaking his head as he trudged off the field with 34 runs to his name.
The hot northwesterly wind stiffened to the degree that the umpires struggled to keep the bails on the stumps but the England bowlers rarely threatened to dislodge those behind Williamson.
The master batsman hit successive boundaries off Bashir to bring up his half-century off 90 balls and, slowly but surely, set about building towards his 33rd test century.