In similar fashion to the pair's previous meeting earlier this season, the home side were two goals to the good by half-time.
While it was Richie Foran and Billie McKay on target for Caley Thistle before the break in Inverness back in August, Lionel Ainsworth and John Sutton put the game beyond the visitors in the return meeting on Wednesday.
In a game of few chances, the hosts made no mistake with their opportunities as Motherwell moved back level on points with second-place Aberdeen.
Rotherham United loanee Ainsworth opened the scoring after 25 minutes, when he showed a burst of pace to evade the Inverness defence and slot home from inside the area.
And eight minutes later, Motherwell were two ahead thanks to Sutton's 18th league goal of the season as the experienced striker got on the end of Steven Hammell's cross to head home.
Iain Vigurs threatened with a lob for Stuart McCall's men after the break while Ryan Christie could have had a brace for Inverness had the ball fallen more kindly for him.
As it was, Inverness could not find a way back and they are now without a win in three league matches ahead of Saturday's clash with Partick Thistle while Motherwell remain in a fight for second.
