In his first game back in Cronulla since testing positive to banned substances while playing for the club in 2020, Xerri scored a try double as the Bulldogs made a clear statement.
Without two of their biggest attacking threats in Viliame Kikau and Matt Burton, the Bulldogs' defence was superb and their kick chase just as good.
Underrated forward Harry Hayes summed up the night when he dived on a kick to deny Cronulla a try in the first half, while Marcelo Montoya made another try-saving play late.
Missing Siosifa Talakai (concussion) and Kayal Iro (hamstring), the Sharks had as much good attacking ball as the Bulldogs but only cracked Canterbury's line once.
The victory left Canterbury the only undefeated team in the NRL after Melbourne's earlier loss to St George Illawarra, winning their first four games for the first time since 1993.
It means the Bulldogs will also end a round in first place for the first time since April 2016, with the club having been to hell and back in the time since.
It came in the highest-quality of the game of the season so far, with emotions regularly boiling over.
Canterbury's chief antagonist Reed Mahoney was placed on report twice, lucky not to be sin-binned for striking Dan Atkinson in the head while on the ground.
Sitili Tupouniua finished the night in the sin-bin for Canterbury, after a late hit on Braydon Trindall.
As tough and gritty as the Bulldogs were, the spark on their left edge proved the difference even without injured duo Burton and Kikau.
Jacob Preston was Canterbury's best, running a good line to score their first try off a Bailey Hayward face ball.
Deputising for Kikau, the second-rower also helped put Xerri over for his first when he collected a ball behind his back and then offloaded inside for the centre.
It would surely have been an emotional moment for Xerri, who has avoided talking about his old team Cronulla since his return to the NRL last year.
A teenage prodigy when he debuted as a speedy centre for the Sharks in 2019, Xerri was handed a four-year ban in 2020 after testing positive to exogenous testosterone.
Moments after giving the Bulldogs the lead when he crossed off the Preston offload, the centre looked as if he had put Montoya over on halftime.
The try was ultimately rebuffed when Xerri was ruled to have grabbed the jersey of Sam Stonestreet, stopping the Sharks winger having a shot at Montoya.
But after Stephen Crichton stepped and spun his way over to make it 14-6 for the Bulldogs, Xerri was not to be denied again.
The centre cut back inside, ran through fullback Will Kennedy and beat two more Sharks defenders to put the final nail in the coffin of his former team.
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