The Portugal forward's first goal - a trademark swerving free-kick - restored Madrid's lead after Marcelo's opener had been swiftly cancelled out by Ramires in the first half, and his second - a fierce header - sealed victory for Carlo Ancelotti's team.
The brace will no doubt have been particularly sweet for Ronaldo, with Mourinho having claimed towards the end of his reign as Madrid boss earlier this summer that his compatriot "maybe thinks that he knows everything and that the coach cannot improve him any more".
Madrid started brightly at Sun Life Stadium and took a 14th-minute lead through Marcelo. The Brazil wing-back was afforded too much space and ran at Gary Cahill before firing a low left-footed shot under the grasp of Petr Cech.
Ancelotti's side were ahead for only two minutes, though, before Ramires rounded off a neat team move in style. The 26-year-old capitalised on a lucky ricochet to burst through the middle and dink a cool finish over Iker Casillas for his third goal of pre-season.
Ronaldo had a couple of early sighters and was rewarded for his endeavours just after the half-hour mark when he unleashed a vintage free-kick high into the Chelsea net. Cech again got fingertips to it but was unable to keep it out.
And the Blues' hopes of getting back into the game suffered a decisive setback 12 minutes into the second half when Ronaldo timed his run to perfection and powered home a header from Isco's cross.
Spain Under-21 striker Alvaro Morata, reportedly wanted by Tottenham as part of any deal to take Gareth Bale to the Bernabeu, thought he had added a fourth goal in stoppage time but his effort was correctly ruled out for offside.
AC Milan earlier clinched third place in the friendly tournament with a 2-0 triumph over the Los Angeles Galaxy courtesy of first-half goals from Mario Balotelli and M'Baye Niang.