Langlois departed from Boston on 14 September 1841 and sailed for the Pacific Ocean via the Cape Horn.[2] Their vessel visited the port of Valparaíso at the end of December, where they waited for 63 days for another ship to continue ferrying them. They then went across Oceania to visit the Gambier Islands and other parts of the Polynesian Triangle. Next Langlois and Bolduc on 5 May 1842 reached the Kingdom of Tahiti. The two priests had a meeting with Queen Pōmare IV to explain their status as British subjects rather than French.[3]
Heading north from Tahiti, on 21 June their ship reached the Kingdom of Hawaii. Greeted by fellow Catholic Louis Désiré Maigret, he informed the two priests that they had to wait several days for the next ship to visit Honolulu, the Hudson's Bay Company barge Cowlitz.[3] On 18 August the Cowlitz left the port of Honolulu for the Columbia River.[4]
Over the next six years Langlois was often stationed at St. Francis Xavier to proselytise among the Cowlitz people.[1] During this time he met members of the Jesuit Order, such as Michael Accolti, John Nobili and Pierre-Jean De Smet, who likely had an influence on him in considering joining the order.[1] Intending to study further in Quebec, Langlois departed from the Pacific Northwest early in 1849.