A string of trucks laden with 150 tonnes of tomatoes rolled through the town's narrow streets, as teams on board distributed the load to surrounding crowds for people to throw at each other during the hour-long morning festivities.
The iconic fiesta, billed at "the world's biggest food fight," has become a major draw for foreigners, in particular from Britain, Japan, Australia and the United States.
Buñol city hall estimates that only one-fifth of the roughly 22,000 participants this year are from Spain.
Buñol mayor Rafael Perez said the event had become so successful by allowing anyone participating to let off steam.
"There are countries where maybe people have a harder time expressing their feelings," he told Spanish radio.
"The Japanese for example are very reserved, solemn, and transform themselves when they come here," he added.
Organizers recommend participants squish the tomatoes before throwing them - "the hit will be less painful" - wear old clothes and use goggles to protect their eyes from the fruit's acid.
This was the third year non-resident participants were charged €10 ($11.50) to take part.
The town of around 10,000 people hired a private company to sell tickets in 2013 to help pay off debts and control the growing crowds who were flocking to the event.
A total of 17,000 tickets were sold to foreigners with the rest given away free to locals.
Before ticket sales were introduced the food fight drew over 45,000 revellers to the town.
The Tomatina started in 1945 when locals brawling in the street at a folk festival seized tomatoes from a greengrocer's stall and let loose.
Today's Google Doodle pays homage to the annual tradition and features an animation of the world-famous food fight.