Goals in each half by Dean Cornelius and Kevin van Veen gave the hosts a deserved 2-0 success which moved them above Dundee United into fourth place in the Scottish Premiership.
Motherwell – receiving good early backing from the boisterous Well Bois fans – hit the front after 17 minutes when Sean Goss’s cross from the left was headed out by Saints defender Jamie McCart to Dean Cornelius who controlled on the chest before smacking the ball home on the half volley for his first ’Well goal.
There was then another chance for the hosts when Stephen O’Donnell’s long ball forward was won by ’Well striker Kevin van Veen against Saints skipper Liam Gordon; the Dutchman’s subsequent goal attempt was blocked behind by defender James Brown.
From Liam Donnelly’s corner, the ball was partially cleared to O’Donnell whose volleyed effort was deflected behind off Callum Booth.
A rare St Johnstone attack then culminated in Liam Craig sending a fierce left footed effort just wide from outside the box.
Normal service resumed when Kaiyne Woolery sent Tony Watt away on the right and his cross was deflected wide off Goss.
Into the second half and the visitors’ Stevie May sent a speculative right footed effort well over Liam Kelly’s crossbar.
But it was Motherwell who were to double their advantage on 55 minutes.
After gathering Sondre Solholm’s ball forward, van Veen turned McCart inside out before blasting the ball through Zander Clark’s legs.
May then broke down the left for Saints and pulled back for Booth whose attempt was tipped over by Kelly.
The last meaningful action saw a Saints corner by substitute Jacob Butterfield eventually arrive with Glenn Middleton whose chipped effort was comfortably gathered by Kelly.
’Well will fancy their chances of making it back to back wins in the league as they host Livingston this Sunday, Boxing Day, with kick-off at 3pm.