Gauthier was admitted to the Quebec bar in 1889 and practised in Montreal, Laurentides and Westmount.
In 1901, he was named King's Counsel.
Gauthier was mayor of Laurentides in 1905.
He was elected to the Quebec assembly in a 1906 by-election held after Joseph-Édouard Duhamel resigned his seat to accept an appointment.
He was defeated by Walter Reed when he ran for reelection to the Quebec assembly in 1908.
Gauthier was defeated when he ran for reelection to the House of Commons in 1921 and was also unsuccessful in federal elections held in 1921, 1925, 1926 and 1930 and in a Quebec election held in 1927.
Gauthier was married twice: to Marie-Amazilie Morency in 1893 and to Marie-Anne Desmarais in 1901.
He died in Montreal at the age of 72 and was buried in the Notre Dame des Neiges Cemetery.