This study aimed to explore the role of democratic decision legitimacy in the formation of consumer attitudes toward drinking water. Using consumer-level data on the decision to change the drinking water sources in two Swedish cities, three core sets of variables were constructed: (1) the overall democratic decision legitimacy, defined as the citizens' support for the decision; (2) the input, throughput and output dimensions of decision legitimacy, representing the citizens' perceived opportunity to provide input, their ability to oversee, as well as their level of satisfaction with the outcome of the decision-making process; and (3) consumer attitudes toward drinking water, comprising trust, risk perception and acceptance. The results of the study provide support for the proposed mechanism that consumers that perceive a decision-making process more positively also tend to support the ultimate decision more, which in turn helps to establish more positive consumer attitudes towards their drinking water. Consequently, democratic legitimacy is an important precursor for building trust. This is particularly important if a waterborne outbreak has negatively impacted consumers' trust in their water, and when political and engineering decisions must be made.