The Brazilian produced a simple finish in the 27th minute and curled in a stunning long-range goal nine minutes after the break.
Mario Balotelli had volleyed the opener after four minutes as Milan continued their mini revival to climb to ninth place, level with Lazio on 42 points.
Clarence Seedorf's Milan have now gone three matches without defeat, a sequence that has offered the Dutch coach a reprieve after media speculation over his future.
"The goals mean a lot and it was a great night for us," said Kaka. "Tonight was a special achievement for me, 300 games and two goals and it was much more than I expected.
"Football is both great and ugly because of the fact everything changes so quickly. I said last week that the dressing room wasn't divided and you saw that tonight."
Chievo, who missed an injury-time penalty through Cyril Thereau, never looked like notching their first win over Milan at the San Siro.
The visitors gave an insipid display and are fifth from bottom on 27 points, three points clear of the relegation zone and one ahead of Bologna who were brushed aside 2-0 by red-hot Atalanta.
Two goals in six first-half minutes from Giuseppe De Luca and Marcelo Estigarribia gave Atalanta their sixth straight victory, a club record run that has lifted them to seventh place on 46 points.
Milan were on top from the start at the San Siro and it did not take them long to open the scoring.
An inswinging Kaka cross was headed out towards the right wing and Adil Rami whipped over a vicious ball that Balotelli expertly glanced home.
Chievo allowed Kaka to celebrate his special night with a gift of a goal just before the half-hour mark.
The defence stood still as Keisuke Honda dinked a delicate pass towards the 31-year-old who had all the time in the world to chest the ball down and roll in his sixth league goal of the campaign.
Honda was then involved in one of the misses of the season as the unmarked Japanese midfielder smashed the ball over from close range after Balotelli had rolled an inviting pass to him at the end of a slick counter attack.
Chievo put up almost no resistance and Kaka soon put the result beyond doubt with a vintage strike, collecting the ball on the edge of the area and curling a sublime shot in off the post.
It capped the sort of high-class performance he has been lacking since his Milan return from Real Madrid in the close season and he was deservedly applauded off when he made way for Robinho with 16 minutes left.
Cristian Zaccardo miscontrolled the ball in the area in stoppage time and clumsily bundled over substitute Thereau who then thumped his penalty against the bar to cap a miserable night for Chievo.
Napoli, in third, host runaway leaders Juventus on Sunday while second-placed AS Roma travel to relegation-threatened Sassuolo.
- Sports & Recreation
- Mario Balotelli
- Clarence Seedorf