It was an emotional night as the Nou Camp witnessed the return to action of Eric Abidal after a year out following liver surgery.
Fabregas commanded the spotlight though, in the injury-enforced absence of Lionel Messi, scoring three and setting up two for Alexis Sanchez as Barcelona romped home.
The home side were also inspired by head coach Tito Vilanova, who was on the Nou Camp touchline for the first time since January after undergoing treatment for cancer.
Abidal's appearance brought the crowd to their feet, with the Frenchman given a standing ovation when he replaced Gerard Pique in the 70th minute.
Mallorca held their own but it was no surprise when Barcelona made the breakthrough with two goals in two minutes.
Fabregas carried the ball from midfield and played a one-two with Alexis before steadying himself and coolly slotting the ball home across goalkeeper Dudu Aouate.
Mallorca's heads went down and in the 22nd minute they found themselves 2-0 adrift. This time Fabregas cut inside on the left of the area before unleashing a shot which Aouate pushed away from goal only for Alexis to follow up and fire home.
In the 37th minute an intricate passing move ended with Fabregas laying a first-time ball off to Alexis on the right of the area which he reciprocated for Fabregas to drill home.
The former Arsenal captain was involved everywhere and a minute later he provided a superb pass over the top for Alexis, who had got between two defenders, controlling the ball with his right before slotting home with his left.
Fabregas wrapped up his hat-trick seconds after the restart when he collected Iniesta's threaded ball and checked inside the defender before slotting home from close range.
A much-changed Real Madrid recovered from another slow start to secure a 5-1 home win over European hopefuls Levante.
But with star names Cristiano Ronaldo, Mesut Ozil and Angel Di Maria initially watching on from the bench they fell behind - for the third successive match - to Michel's 31st-minute strike.
The response was swift, however, as Gonzalo Higuain hooked in before a Kaka penalty sent Madrid ahead within eight minutes of falling behind.
Ronaldo was inserted at the break and killed the game off after 84 minutes before Ozil added two more to lift Madrid four points clear of third-placed city rivals Atletico.
Real Sociedad opened up a four-point lead on their rivals for fourth place with a resounding 4-2 win at home to Malaga.
The hosts took a commanding lead in the first half thanks to a frenetic nine minutes in which they found the net three times, through Carlos Vela, Alberto de la Bella and Antoine Griezmann.
Pedro Morales pulled one back for Malaga before the break, but any hope of a comeback was then vanquished by a goal by Inigo Martinez shortly after the re-start.
Roque Santa Cruz scored a second consolation goal with 20 minutes remaining, but a home victory was never in doubt.
Deportivo La Coruna gave their hopes of avoiding relegation a fillip on Saturday evening by beating fellow strugglers Real Zaragoza in a 3-2 thriller at the Riazor.
Bruno Gama put the Galicians ahead early in the first half but Helder Postiga levelled from the penalty spot and then Paco Montanes put Manolo Jimenez's visitors ahead.
Carlos Marchena equalised before half-time and Depor took the lead for a second time 10 minutes into the second half thanks to an own goal by Abraham Minero, whose night was made even worse when he was sent off with nine minutes remaining.
On Friday, Real Betis continued their excellent run of form as they swept aside Granada with a dominant 5-1 win at Estadio Nuevo Los Carmenes.
Saturday's La Liga Results
Friday's La Liga Results