Alexander Dennis workers in Camelon and Larbert are walking out in a dispute over pay.
Members of the Unite trade union are staging 11 days of industrial action, as part of the pay dispute.
Workers rejected what they called a "pitiful" pay offer.
An offer, which would increase their wages by 6.6% from next month, was turned down by the union.
Unite says the proposal is a "significant" real terms pay cut.
Pat Egan, Unite industrial officer said; “Unite has engaged ADL in direct talks for months now to find a resolution to this pay dispute. However, despite having a very healthy order book, the company refuse to make our members an offer which their world class work deserves. Our members have been forced by the company to take this strike action and they will continue to take action until the company sees sense.”
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