The 24-year-old Belgian midfielder, who rejoined the Saddlers for a third time last summer, has played 20 times for the League One club this season.
"It's a fantastic signing," said Walsall boss Jon Whitney. "He's an important player. He's the type of person you can build your team around."
Cuvelier is currently sidelined until April, having not played since 14 February because of a calf injury.
Young defender Kory Roberts, 19, and his fellow teenager midfielder, Jordon Sangha, also 19, have also signed new deals, which tie them to the Banks's Stadium until 2019.
Florent Cuvelier has signed a one-year contract extension with Walsall.