This paper develops a decision-support model for transit-based evacuation planning under demand uncertainty. Demand uncertainty refers to the uncertainty associated with the number of transit-dependent evacuees. A robust optimization model is proposed to determine the optimal pick-up points for evacuees to assemble, and allocate available buses to transport the assembled evacuees between the pick-up locations and different public shelters. The model is formulated as a mixed-integer linear program and is solved via a cutting plane scheme. The numerical example based on the Sioux Falls network demonstrates that the robust plan yields lower total evacuation time and is reliable in serving the realized evacuee demand. Copyright © 2012 John Wiley & Sons, Ltd.