The tribunal accepted Sinner's explanation that the anabolic agent clostebol entered his system from a member of his support team through massages and sports therapy, the ITIA said in a statement.
It added that Sinner bears no fault or negligence after his physio Giacomo Naldi applied an over-the-counter spray containing clostebol to his own skin to treat a small finger wound caused by a scalpel used to treat foot calluses.
According to the evidence, Naldi then administered massages to Sinner between March 5th to 13th without using gloves, unaware that the product he had used on his cut contained clostebol.
Sinner's first positive sample was taken on March 10th with a second eight days later.
Provisional suspensions are normally applied in such circumstances under the WADA code, but Sinner was allowed to continue playing after his team filed urgent appeals stating that he had been the victim of contamination.
The ITIA, following consultation with scientific experts, agreed that Sinner's explanation was credible and lifted the provisional suspension ahead of its investigation.
"After each positive test, a provisional suspension was applied. On both occasions, Sinner successfully appealed the provisional suspension and so has been able to continue playing," ITIA said in a statement.
"However, in line with the WADC (World Anti-Doping Code) and TADP (Tennis Anti-Doping Programme), Sinner's results, prize money and ranking points from the ATP Masters 1000 event at Indian Wells, where the player tested positive in competition for clostebol, are disqualified. "
The decision is subject to appeal by the World Anti-Doping Agency (WADA) and the Italian Anti-Doping Agency.
"As we do with all cases, we will review this decision carefully and we reserve the right to take an appeal to CAS (Court of Arbitration for Sport), as appropriate," WADA said in a statement.
Full cooperation
Sinner, who won the Cincinnati Open on Monday, said the independent tribunal had cleared him after he fully cooperated in the ITIA's investigation.
He said in a statement the amount of clostebol found in his system was less than a billionth of a gram.
Clostebol is a steroid that can be used to build muscle mass.
“I will now put this challenging and deeply unfortunate period behind me," Sinner said on X.
"I will continue to do everything I can to ensure I continue to comply with the ITIA's anti-doping programme and I have a team around me that are meticulous in their own compliance."
Responding to the decision, the men's ATP Tour noted the verdict, saying "integrity is paramount" in sport.
"This has been a challenging matter for Jannik and his team, and underscores the need for players and their entourages to take utmost care in the use of products or treatments'" it said.
Sinner is the latest high-profile tennis player to become embroiled in a doping case.
Former Wimbledon champion Simona Halep was cleared to return to competition earlier this year after appealing to sport's highest court CAS against a four-year ban after testing positive for prohibited blood-booster roxadustat at the 2022 US Open.
Halep argued she had unwittingly ingested the substance through contaminated nutritional supplements.
Australian player Nick Kyrgios lambasted the ruling on X, however.
"Ridiculous - whether it was accidental or planned. You get tested twice with a banned substance… you should be gone for 2 years. Your performance was enhanced," Kyrgios wrote.
Australian Open champion Sinner will play in the US Open later this month, with the main draw starting on August 26th.