The 29-year-old moved from Derby County to Walsall last summer and made 23 appearances for the club despite suffering a couple of injuries.
"I'm pleased to get my contract sorted. I was very keen to stay here," said Boertien.
"It's a good club with some talented young players coming through who'll only benefit from their experiences over the past season.
"With the right manager and the right signings, there's no reason why we can't push on and do very well next season.
"There's a lot to look forward to here. It's a fresh start for everyone and, with the new training ground almost in place, it's an exciting time to be involved with the club."