Born into a wealthy Parisian family in late May 1606, Charles Garnier entered the Jesuit novitiate in Paris on September 5, 1624. He completed his philosophy and theology studies at the Jesuits college of Clermont, and was ordained in 1635.
One year later, over his father's objections, Charles was appointed to the Canadian mission to the Huron people. On April 8, 1636, Charles left France in the company of Isaac Jogues and the other missionaries. The group landed in Quebec on June 11, 1636 and proceeded to the mission colony, Three Rivers, on July 1st. The group arrived at Ihonativia, on August 13th and was met by fellow Jesuit, Jean de Brébeuf. In his first letter to his father in France, Charles wrote: "There is no place on earth where I could be happier." In 1638, Charles was assigned to the Jesuit mission in Ossossané.
One year later, in November 1639, Charles and Isaac Jogues were sent to the Petun tribe. This group was hostile to the Jesuit missionaries whom they accused of having caused the epidemic of 1636. Fathers Charles and Isaac remained with the Petuns for several months, but considered their stay a failure. In spite of this disappointment, Charles returned to the Petuns with fellow Jesuit, Father Pierre Pijart, in autumn 1640. The length of their stay is not known, but they faced disappointment once again. The next reference to Garnier in the correspondence with France situates him with the Huron Christians in Saint-Jacques from 1644 to 1646.
In the winter months of 1647, Father Garnier and Father Leonard Garreau went back to the Petuns, and found them more responsive. The Jesuits succeeded in building a chapel and baptizing 184 members of the tribal community.
The Iroquois tribe went to war against the Petuns in November 1649; Charles Garnier was killed in the incursion and raid.
Charles Garnier was beatified by Pius XI on June 21, 1925, and canonized by the same Pope on June 29, 1930.