Danny Grainger's 30-yard strike secured Hearts' first league win at Tynecastle since the opening day of the season.
The former St Johnstone left-back was given time and space to fire past Darren Randolph in the Motherwell goal.
Both sides felt they should have had penalties, but referee Willie Collum was unmoved by the claims.
Well's Nicky Law had a header cleared off the line as Hearts' win moved them up to eighth and Well stay sixth after their first away league defeat.
Motherwell knew that a win would move them in to third place in the Scottish Premier League and they made a bright start, goalkeeper Jamie MacDonald touching Jamie Murphy's 20-yard shot wide.
Hearts' Arvydus Novikovas was proving dangerous and, as he collected Andy Driver's pass and drove into the box, the Lithuanian appeared to be caught by Shaun Hutchison but elected to stay on his feet and his touch took him away from goal and the chance was gone.
The home team continued to have the upper hand and Englishman Driver was next to try his luck, his curling effort going just wide from the edge of the box.
Hearts had not lost three consecutive matches at Tynecastle since December 2007 and were not to be denied, going ahead within 15 minutes.
A quickly taken free-kick allowed left-back Grainger to advance from just inside the Motherwell half and he unleashed a left-footed thunderbolt to leave goalkeeper Randolph with no chance.
The hosts were dominant and Ryan Stevenson's header was deflected wide from a Grainger cross.
Stuart McCall's side finally managed an effort on target after almost 25 minutes. Hearts were claiming handball as Michael Higdon laid the ball back to Murphy, whose effort was comfortably saved by Hearts goalkeeper MacDonald.
It was the visitors who were enjoying the bulk of the possession now, but they were also struggling to create any clear openings and Keith Lasley and Humphrey both fired wide.
Motherwell felt they should have had a penalty when Andy Webster bundled Higdon over in the box. Referee Collum decided the Hearts' defender won the header cleanly.
The same pair were involved shortly after at the opposite end, Webster evaded Higdon, but he could not make a proper connection and failed to trouble Randolph.
Higdon nearly drew his side level early in the second half after being found by Humphrey, but his shot flashed just wide of the target.
The second 45 lacked the same fluency as the first, but Ryan Stevenson was next to go close, his drive from 30 yards going a whisker wide of the junction of the post and the bar.
Grainger nearly gifted Well an equaliser when he was robbed by Humphrey, who fed Higdon - the former St Mirren striker's effort was straight at MacDonald in the Hearts goal.
Substitute John Sutton should have put John McGlynn's team two goals ahead after 68 minutes, but his header dropped inches wide of the post.
Motherwell thought they were level with around 15 minutes to play, but Webster was on hand to clear Law's header off the line.