Winger Chris Humphrey, whose partner gave birth to a girl on Thursday, brilliantly created second-half goals for Nick Blackman and John Sutton.
Hearts never troubled Motherwell goalkeeper Darren Randolph and the visitors comfortably secured their fifth away clean sheet and win of the season.
Rudi Skacel made his return to Hearts action after rejoining the club this month but he was totally overshadowed by a convincing second-half display by the visitors, who took the lead in the 58th minute, seconds after the Czech midfielder came off the bench.
Darren Barr was left out of the Hearts squad after manager Jim Jefferies criticised the defending during his side's 4-3 defeat by Falkirk in the midweek Co-operative Insurance Cup clash.
Adrian Mrowiec came in at centre-back while Jason Thomson replaced namesake Craig, who was sent off at Falkirk, at right-back but it was skipper and left-back Eggert Jonsson who failed to deal with Humphrey's ever-increasing threat.
Motherwell named the same team that drew with Aberdeen last weekend with Steve Jennings, Keith Lasley and Jamie Murphy back after being rested for the cup win at Brechin. Hearts wide men David Templeton and Suso Santana made a lively start and twice combined to fashion shots at goal, although both players were off target.
Motherwell took some time to settle into their passing game but improved after the first 20 minutes.
However, Templeton created a good chance in the 30th minute when he manoeuvred himself out of a tight spot near the corner flag and crossed for Kevin Kyle, who headed on to the roof of the net from 12 yards.
Motherwell created the best chance of the half five minutes later on the counter-attack. Hearts midfielder Ryan Stevenson looked a clear favourite to reach Darren Randolph's kick-out following a Hearts corner but Humphrey outsprinted him and showed good composure to lay the ball back for Blackman.
Keith Lasley flicked on the striker's pass to the unmarked Jamie Murphy, who elected to shoot first time from 16 yards but saw his effort curl off the post.
Murphy soon came close again with a powerful 25-yard strike with the outside of the boot, which was acrobatically touched past the post by Marian Kello.
Motherwell finished the half well, although Hearts had a hopeful penalty appeal rejected when Stephen Craigan tackled Calum Elliot.
Murphy forced another good save after the break after being allowed to run at the heart of the home defence and unleash a well-hit strike from 25 yards.
Steven Saunders was booked for a trip on Templeton 25 yards out but Elliot curled the resulting free-kick over the bar.
The home fans were lifted when Skacel came on and Stephen Elliott made his first appearance since the opening day of the season after recovering from a hamstring injury.
But they were silenced within 60 seconds. Hateley broke and found Humphrey, who beat Jonsson and crossed for the unmarked Blackman to guide a cushioned volley into the corner of the net from six yards.
Thomson was booked for a wild challenge on Murphy but soon made a more positive contribution when he crossed for Kyle, who looked certain to score from four yards until Mark Reynolds ghosted past him to make a superb clearance.
Motherwell came close again when Kello spilled Lasley's 20-yard drive but recovered to divert Sutton's follow-up over the bar, although referee Mike Tumilty gave a goal kick.
But Sutton was soon celebrating in the 70th minute. Humphrey again skinned Jonsson and ran along the byline before driving the ball into the goalmouth for Sutton to tap in.
Hearts never looked like getting back in the game and Kello remained busy, denying Blackman from close range before saving long-range efforts from the on-loan Blackburn striker, Hateley and substitute Ross Forbes.