Mercedes were called to see the race stewards immediately after Hamilton romped to victory in Monza.
After a near two-hour investigation they reached a verdict to allow Hamilton to keep his victory.
It means Hamilton will head to the Singapore Grand Prix with a 53-point lead over Nico Rosberg who retired with an engine problem.
As Hamilton celebrated on the podium, his emphatic victory was cast in doubt after Mercedes were called to see the race stewards.
A technical delegate report issued by the FIA, the sport’s governing body, claimed Hamilton’s left-hand side rear tyre was ”0.3 psi below the minimum tyre starting pressure”.
Rosberg, who retired with only two laps remaining, was also under investigation.
Representatives from Mercedes reported to the stewards at 3.15pm Irish time and the FIA’s final decision was revealed shortly before 5pm.
Their statement read: “Having heard from the technical delegate, the team representatives, and the Pirelli team tyre engineer, the stewards have determined that the pressure in the tyres concerned were at the minimum start pressure recommended by Pirelli when they were fitted to the car.
“In making this determination regarding the pressures, the stewards noted that the tyre-warming blankets had been disconnected from their power source as it is normal procedure and the tyres were significantly below the maximum permitted tyre blanket temperature at the time of the FIA’s measurement on the grid, and at significantly different temperatures from other cars measured on the grid.
“Further, the stewards are satisfied that the team followed the currently specified procedures, supervised by the tyre manufacturer for the safe operation of the tyres. Therefore the stewards decided to take no further action.
“Nevertheless, the stewards recommend that the tyre manufacturer and the FIA hold further meetings to provide clear guidance to the teams on measurement protocols.”
Hamilton was urged by his team to post a number of quick laps in the final stages of the race. “We will explain later,” his race engineer Peter Bonnington said with Mercedes seemingly fearing a post-race penalty. He crossed the line 25 seconds clear of Sebastian Vettel.
Hamilton headed into yesterday’s race having topped every practice and qualifying session. He followed that up with a lights-to-flag victory and posted the fastest lap, too.
“It has been a perfect week-end for me,” said Hamilton, who claimed his 40th career win, just one shy of Ayrton Senna’s tally.
Monza is known as the temple of speed, but for Rosberg it was more the temple of doom. The German, who had already reverted to an inferior Mercedes engine after his packed up in practice on Saturday morning, started from only fourth on the grid.
After Kimi Raikkonen’s anti-stall appeared to kick in off the start line and he failed to get away, Rosberg, who had to take evasive action, was promptly gobbled up by the Williams duo of Massa, Valtteri Bottas, and Force India’s Sergio Perez to leave him sixth.
Rosberg clawed his way back to third and was within two seconds of Vettel on his Ferrari debut in Italy when his engine packed up. Massa held off Bottas to take the final spot on the podium.