The gold medal followed on from the bronze the 16-year-old had won the day before in the men’s individual platform competition.
Dixon and Williams were a class above their rivals in Gatineau, Quebec.
The Great Britain pair scored an impressive 406.32 points. That was more than 50 points ahead of France’s Alexis Jandard and Lois Szmczak, who finished second with 348.84.
America’s Jordan Windle and Ryan Hawkins took third with 335.67.
Dixon could possibly be back in action in his home city on Wednesday.
The Plymouth Studio School pupil is among the entries for the boys’ A platform event at British Elite Juniors, which are being held at the Life Centre.
Plymouth Diving made a good start to those championships on Sunday with Euan McCabe and Alfie Westerman winning synchro silver in the boys’ 9-13 year-old three-metre final.
They scored 209.64 points to finish behind Southampton’s Robbie Lee and Milo French, who scored 219.48.
Plymouth Diving have 12 young athletes in action at the championships which run through to Wednesday.