De Tournon was born in Turin, Italy. In 1701 he was appointed patriarch of Antioch and apostolic visitor by Pope Clement XI, who wanted to settle the controversies about the Malabar Rites and the Chinese Rites. De Tournon reached Pondicherry, India, in November 1703 and in 1704 issued instructions condemning the Malabar Rites. He proceeded to Manila to settle some ecclesiastical affairs.
In April 1705 he entered Macao and then Canton (Guangzhou), where he held discussions about the rites issue with missionaries of various religious orders before proceeding to Peking (Beijing). In two audiences, December 1705 and June 1706, de Tournon replied evasively to the K'ang-hsi emperor's request to issue a decree settling the rites, since he did not want the emperor involved in such religious matters.
In poor health and unsuccessful in the negotiations, de Tournon left Peking and stopped in Nanking (Nanjing), where in January 1707 he issued an edict against the Jesuit accommodation policy. This nullified the emperor's 1706 decree allowing missionaries to stay in China with a residence permit provided they followed the interpretations of Matteo Ricci on the rites. Subsequently the emperor banished de Tournon to Macao, where under house arrest he received papal appointment as cardinal shortly before his death.