Flight KL685 was thousands of feet over Canada when activity from the volcano Popocatépetl near the Mexican capital forced it back across the Atlantic.
Passengers spent 11 hours in the air, only to disembark in the same city.
A KLM spokeswoman told the BBC the plane was also carrying a large number of horses at the time.
The spokeswoman could not be drawn on exactly what caused the captain to turn back to the Netherlands, saying there were "many reasons" behind such decisions, but admitted the equine cargo may have been a factor.
KLM has apologised for the inconvenience and rebooked flights for all passengers.
The flight, which set off at about 15:00 local time (14:00 GMT), arrived back at Schiphol airport at 02:30 the next morning "where the passengers have been cared for and have been rebooked," a KLM statement said.
"Our operation to Mexico will run on schedule again as of today," the airline said.
Maps of the plane's flight path posted online show it was over New Brunswick in Canada when it turned around.