Why do workers decide to go on strike or change their mind during a strike? This field study aims to determine to what extent employees' perceptions of justice formed during the collective bargaining process influence their strike vote. Data were collected from a North American university faculty that went on strike 21 months after the expiration of its collective agreement. The results show that perceived justice about collective bargaining is a determinant of the strike vote. The role played by the employer and the union as a source of (in)justice and the importance of the four types of justice perceptions (procedural, distributive, interpersonal, and informational) vary depending on the context of ballots (initiate, continue, or end the strike). This suggests that the reduction of uncertainty leads to the activation of three different mechanisms: judgmental heuristics (salience), social comparison, and cognitive dissonance. The results also suggest that employees attempt to be as rational as possible when they decide to go on strike. Nevertheless, the decision to join strikers and to continue the strike is partly based on an emotional process: employees use the strike to punish the employer. Copyright © 2012 John Wiley & Sons, Ltd.