Goals in each half from Matty Smith and Nahum Melvin-Lambert was enough to overcome an in-form Waterford at Richmond Park on Friday night.
Junior Quitirna scored Waterford's second-half goal from the penalty spot to give Stephen O’Donnell’s side a late scare.
The Saints held firm though, solidifying the win and drawing level on points with league-leaders Shamrock Rovers, albeit having played two games more.
However, events on the pitch were nearly overshadowed by a late horror injury to St Pat's defender Lee Desmond who suffered a head collision and collapsed in the game’s final moments.
Things got even uglier as tempers flared among the crowd and sideline as the players began confronting each other over the reaction to the injury and resulting free-kick.
Concurrently, the crowd roared at what they perceived was a slow reaction from paramedics as the player was urgently placed into the recovery position by his teammates.
Thankfully, the night finished with good news as Desmond appeared to regain consciousness before being stretchered from the pitch.
St Pat's started the brighter of the two sides, focussing their attention down the right-wing towards the combination of Sam Bone and Billy King.
Scottish winger King had the first chance of the game when he charged inside, beating two players before unleashing a shot just wide of the Waterford near post.
While Waterford struggled to construct clear-cut chances in the first half, they did display elements of danger through the link-ups of Junior Quitrina and Prince Mutswunguma. A much-needed final product, however, was missing throughout the half.
The Saints deservedly opened the scoring in the 23rd minute. It was King again who managed to turn into space in midfield before attempting to lay the ball off to Melvin-Lambert.
Defending, Niall O’Keeffe managed to poke the ball away from the Saints striker but only into the path of Smith who struck it low and hard past Brian Murphy.
However, the celebrations were cut short for the former Rangers man when he pulled up with an injury and was substituted for Darragh Burns just minutes after scoring.
The Saints had another chance five minutes later when Eddie Nolan took down Ben McCormack on the edge of the box. Murphy did well to save the Paddy Barrett's resulting free-kick.
Minutes later the Blues had their greatest chance yet to equalise. Dispossessing Barrett in the back line, Quitirna suddenly found himself charging unchallenged towards goal but couldn’t keep his composure as he struck a shot into the terraces behind.
It was a big let off, and just moments later the Saints capitalised with a goal to double their lead.
Ian Bermingham was the creator as he drove the left flank before floating a cross onto the head of Melvin-Lambert to flick home from three yards.
Seeking to solidify the home side’s lead, O’Donnell introduced Jamie Lennon to shore up proceedings and provide extra protection in front of his two central defenders.
However, Waterford were not willing to let themselves go through the motions of being two goals down. Marc Bircham's side reignited their hopes from the penalty spot on the 63rd minute.
Not dispirited by his miss earlier in the half, Quitirna took the ball past Lennon with an eloquent turn before being fouled by Desmond just inside the box.
This time the 21-year-old made no mistake as he stroked the penalty inside the left post.
Suddenly the hosts looked more nervous than assured by their one-goal lead. With Pat’s continuing to play Bone and Bermingham in higher full-back positions, Waterford began to see space every time they gained possession.
That said, clear chances remained elusive as Pat’s slowly regained their composure.
Waterford were pushing forward with long balls into the box when Desmond suffered his apparent concussion in the 90th minute.
A lengthy stoppage ensued as the player received medical attention from a host of paramedics before being stretchered off.
With tempers flaring up and the crowd increasingly restless, the game was just allowed to restart before the final whistle confirmed all three points for the Saints.
St Patrick's Athletic: Vitezslav Jaros; Sam Bone, Lee Desmond (Sam Curtis, 97), Paddy Barrett, Ian Bermingham; Chris Forrester, Alfie Lewis (Jamie Lennon, 61), Ben McCormack (Jason McClelland, 73); Billy King, Matty Smith (Darragh Burns, 26); Nahum Melvin-Lambert (Ronan Coughlan, 73).
Waterford FC: Brian Murphy; Darragh Power, Cameron Evans (Kyle Ferguson, 67), Shane Griffin, Junior Quitirna; John Martin, Niall O'Keeffe (Greg Halford, 72), Jack Stafford, Prince Mutswunguma (Isaac Thipamba, 72), Phoenix Patterson (Cian Kavanagh, 46), Eddie Nolan.
Referee: John McLoughlin