Inter Milan striker Adriano has escaped a possible two-game ban after scoring the opener with his arm in Sunday's 2-1 win over AC Milan.
There was insufficient proof that the Brazilian had deliberately intended to commit a handball, the Italian league's disciplinary unit said in a statement on Tuesday after reviewing video evidence.
The ball came off his head and then hit his arm before flying into the net in the 28th minute following Maicon's cross.
A similar incident happened in October when Fiorentina's Alberto Gilardino was banned for two games after it was decided he had deliberately used an arm to score in a 3-1 win at Palermo.
Sunday's tight win moved Inter nine points clear at the top of Serie A and left third-placed Milan 11 adrift and virtually out of the title race.
Inter President Massimo Moratti has said the champions would have won anyway despite the handball but Milan coach Carlo Ancelotti said the incident had been crucial.
Milan chief executive Adriano Galliani bit his tongue as his side flew out for Wednesday's UEFA Cup game at Werder Bremen.
"Many successes have taught me to stay quiet when we lose and let those who win speak. But everyone has eyes to see..," he told reporters.
Adriano, who had a series of run-ins with coach Jose Mourinho in the first half of the season, had only just returned from a three-match ban for throwing a punch in a 1-0 win over Sampdoria where he also scored.