The Irishman scored in each half to move St Johnstone level on 12 points with opponents Hearts in the top six, with both teams sharing identical goal difference.
Sheridan twice latched on to passes from striker partner Francisco Sandaza to breach a one-dimensional Hearts defence and leave Paulo Sergio's men without an away win this season.
The link-up play between the two summer signings was in stark contrast to a blunt Hearts attack, with Stephen Elliott receiving little meaningful support from Sergio's attacking midfielders.
Only Marius Zaliukas and Danny Grainger kept their place after the visitors' midweek Scottish Communities League Cup defeat by Ayr, when Sergio made eight changes, with Andy Webster returning after injury.
David McCracken and Kevin Moon returned from injury for St Johnstone while Willie Gibson came into the team, with Frazer Wright missing out after tearing a calf and Sean Higgins and Jamie Adams dropped following the cup defeat by St Mirren.
Neither team could get in behind their opponents in an even opening spell but Saints midfielder Chris Millar came close with a rising long-range strike.
Sandaza turned Webster 25 yards out in the 19th minute and was pulled back by the Hearts centre-back, but referee Stevie O'Reilly decided a yellow card was sufficient with a Hearts player covering.
The resulting free-kick gave Liam Craig the opportunity to shoot and Jamie MacDonald pushed the strike over.
St Johnstone were rewarded for a period of pressure in the 30th minute.
Sandaza created the opening when he took the ball in and played an instant pass for Sheridan to run on to past a high Hearts back line. The Irishman kept his composure and struck the ball high into the net from the edge of the box.
The hosts should have been two ahead when Sheridan guided a high ball into the path of Craig's run, but the midfielder scuffed his shot from 12 yards and the ball bounced just wide.
Former Saints left-back Grainger almost silenced the home fans, who were giving him a hostile reception, when he curled a 35-yard free-kick towards the far corner but Peter Enckelman got down well to hold.
Enckelman soon came and missed Grainger's deep corner but Ryan Stevenson could not direct his header on target from a tight angle.
Webster did not reappear for the second half. David Templeton came on and Adrian Mrowiec dropped back, with David Obua moving into the centre of a five-man midfield.
St Johnstone escaped unscathed following dangerous crosses from Jamie Hamill and Grainger and they extended their lead in the 55th minute with a similar goal to the opener.
Sandaza collected the ball midway inside the Hearts inside and rolled it into the path of Sheridan, who burst through a gaping hole in the Hearts defence, rounded MacDonald and stroked the ball into the net.
Hearts brought on youngsters Gordon Smith and Scott Robinson for Obua and Elliott but they struggled to make their possession count and it was a mistake by Enckelman that almost gave them a lifeline.
The goalkeeper spilled Hamill's speculative left-footed effort and Hearts kept the pressure on. Templeton could not get hold of his volley but Ryan Stevenson diverted the shot with his head, however Enckelman redeemed himself with a diving one-handed stop.
Hearts pushed more men forward but they could not find a breakthrough and Ian Black showed his frustration when catching David Robertson late as he became the seventh player to be booked by the pernickety O'Reilly..