The Brazilian combined with Mario Balotelli nine minutes after the interval, sending a sumptuous curling effort into the top right corner in a true moment of quality in an otherwise dour affair.
It was Kaka's first goal of the season, and one incredibly similar to a strike he netted against the same opponents in a 4-1 win back in September 2008.
But it was not enough for Milan to seal three points as Mickael Ciani headed home from an Antonio Candreva cross with 18 minutes to go to secure his side a point.
Kaka was given just his second league start of the season as Massimiliano Allegri made four changes from Sunday's 3-2 defeat at Parma, while Lazio boss Vladimir Petkovic also rotated heavily.
Just five Lazio players who started the club's 2-0 win over Cagliari survived, with German striker Miroslav Klose – who came off the bench to score on Sunday – among the new inclusions.
Balotelli, who came in for criticism from Allegri after his performance on Sunday, tested Lazio goalkeeper Federico Marchetti as early as the second minute, driving into space before unleashing a shot from 25 yards which the goalkeeper parried low to his right.
Kaka was next to threaten for the hosts, fizzing an effort narrowly over the bar from 20 yards in the 14th minute following a swift counter-attack.
The Brazilian went even closer four minutes later, dragging his shot just wide of the left post after being found inside the box by Sulley Muntari.
As the half wore on the home side assumed total control, but Milan's Riccardo Montolivo saw two thumping drives easily handled by Marchetti.
Klose wasted Lazio's first real chance of the game five minutes after the break, with the veteran's touch letting him down when better control would have seen him with just Milan goalkeeper Gabriel to beat from eight yards.
Four minutes later Kaka put Milan in front, receiving Balotelli's pass from the left before curling an unstoppable shot beyond a helpless Marchetti from 20 yards.
It was not enough to stop the visitors though, who despite showing little attacking threat, equalised with 18 minutes to go.
French defender Caini was the scorer, rising unchallenged to glance home Candreva's cross from the right from six yards.
Klose, with eight minutes to go, had a chance to secure Lazio's first away league win against Milan since August 1989, but his tame effort was straight at Gabriel, as both sides shared the spoils.
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