Stevie May and Nigel Hasselbaink were both on the score sheet with second-half goals in the clash at McDiarmid Park in front of just 2,449 fans.
Paddy Cregg and Tom Scobbie were added to the St Johnstone starting line-up for the visit of Well, replacing the suspended Frazer Wright and the injured Steven MacLean.
New signing Sanel Jahic was named on the bench after penning a short-term deal earlier in the week.
The home side enjoyed the better start to the game and Cregg saw his shot flash wide from 18 yards in the opening minutes after being teed up by Hasselbaink.
Brian Easton then picked out David Wotherspoon in front of goal but his header was deflected past the post for a corner that Saints failed to capitalise on.
At the other end, Well came close with the best chance of the first half when John Sutton threw himself in front of a decent cross from Simon Ramsden and nodded on the wrong side of the upright.
With half-time approaching and the match still deadlocked, Wotherspoon resorted to a shot from distance that was off-target and did little to trouble Gunnar Nielsen in the Motherwell goal.
Saints then passed up another chance to open the scoring before the break when the ball broke for Gary McDonald in front of goal and he connected awkwardly and finished poorly.
The breakthrough came four minutes after the restart when the home side surged into the lead.
Nielsen produced a great save to prevent McDonald's impressive overhead kick from finding the back of the net but May pounced to slot home the rebound from close range.
Motherwell could have been back on level terms but goalkeeper Alan Mannus came to the rescue with a point blank save to deny Shaun Hutchinson from six yards out.
Instead, it was Saints who had the net bulging again on 64 minutes.
Nielsen slipped on the slick surface while trying to deal with a Ramsden passback, allowing Hasselbaink to claim possession and rifle into the far bottom corner.
Hasselbaink could have claimed his second of the day when he collected a fine pass from May and found himself one-on-one with Nielsen, but the keeper went some way to making amends with a decent block.
- Sports & Recreation
- Nigel Hasselbaink
- David Wotherspoon