Audrey and Noemi Belanger, aged 20 and 25, were found dead on June 15 in the Phi Phi islands.
A funeral was held Saturday afternoon at a church near Pohenegamook, in eastern Quebec where the pair grew up.
The presiding priest said it was an opportunity to reflect on the sisters' lives.
"It will be a sombre celebration, but it will also leave a message of hope," said Father Jean-Roch Castonguay.
Police have said the women didn't appear to have been murdered and evidence suggests they may have been accidentally poisoned.
Autopsies were performed on the bodies in Montreal in late June.
Experts say it might be some time before the family can know for sure what caused the deaths, and whether a toxic substance was indeed involved.
The sisters studied in Quebec City with their eldest sister, but also worked at the family store in the community of roughly 3,000.