The tour operator has pledged to offer all its travellers to the islands a reusable bottle from January 1, 2019.
Plastic bags were outlawed on the islands in May and plastic bags on Thursday (July 26).
And as of February 26 next year, non-returnable plastic bottles of any description will be banned too.
G Adventures operates more than 30 land and sea Galapagos itineraries.
Managing director Brian Young welcomed the move, adding plastic waste had reached ‘critical levels” globally.
“As a responsible tour operator, we have more responsibility to protect our planet than ever before," said Young.
