First-half goals from Alan Gow and Nicholas Blackman secured the win at Tulloch Caledonian Stadium, despite a late fightback from the hosts who reduced their arrears through Stuart Duff.
A fourth home league defeat for Inverness, coupled with Dundee United's win at Hamilton, sees the Highlanders slip to fifth in the league.
Inverness goal hero Eric Odhiambo, who scored the late leveller in the 1-1 draw against Rangers last Saturday, was part of a strong attacking line up alongside the Irish trio of Adam Rooney, Richie Foran and Jonny Hayes.
Odhiambo came in for Russell Duncan, who was left out of the squad, while midfielder Lee Cox recovered from an ankle injury to be named as a substitute, his first inclusion since the end of September.
Motherwell brought in striker John Sutton for midfielder Ross Forbes in their only change to the side which lost 1-0 at home to Hamilton last weekend.
Both sides showed attacking intent in the opening stages and Nick Ross might have opened the scoring for Inverness after just three minutes, but his low shot from the edge of the box went inches wide.
Goalkeeper Ryan Esson prevented Sutton from breaking the deadlock moments later when his low first-time shot was pushed wide after being found by Chris Humphrey.
Stephen Craigan was on target with a header from a Tom Hateley free-kick, but Esson saved again.
Hayes picked out Foran who was one-on-one with Darren Randolph, but the goalkeeper was equal to it.
Randolph was at full stretch to deny Hayes midway through the half when the Irishman's low drive was tipped wide after he cut inside the area.
Esson was next to be called into action when he parried out Blackman's thunderbolt after Ross was caught in possession.
Esson made another top drawer diving save on the half-hour to prevent Hateley's 25-yard free-kick finding the net.
But Esson was finally beaten when Gow netted from close range with a header following a goalmouth scramble after Humphrey's clever short corner with Hateley.
Blackman doubled the lead on 43 minutes when his shot from 30 yards took a wicked deflection off defender Grant Munro and looped over a stranded Esson into the net.
Blackman squandered the opportunity to extend Motherwell's lead after the break when he latched onto a Steven Jennings through ball.
With support either side and attackers outnumbering defenders, the on-loan Blackburn striker lifted his shot over the bar.
Gow could have had his second just after the hour but directed his header wide when he connected with a Jennings cross.
Rooney powered a header just over with 20 minutes to go after Duff's quick free-kick played in centre-back Ross Tokely, who provided an inch-perfect cross to the striker.
Inverness finally broke through Well's rearguard when Duff's 25-yard drive on 74 minutes found the bottom corner after Rooney's lay-off.
Inverness substitute Shane Sutherland shot just wide from distance after beating Craigan as the hosts hunted for an equaliser in the closing stages.