The human dimensions of harmful algal blooms (HABs) are becoming increasingly apparent as they grow in frequency and magnitude in some regions of the world under changing ocean conditions. One such region is the U.S. West Coast, where HABs of toxigenic species of Pseudo-nitzschia have been found to coincide with or closely follow periods of warming. In 2015, the region experienced a massive HAB of Pseudo-nitzschia that was associated with the 2014-16 Northeast Pacific marine heatwave. The HAB event delayed the opening of the lucrative commercial Dungeness crab fishery for up to 5 months and closed the popular recreational razor clam fishery, resulting in fishery failures and disaster declarations and causing significant sociocultural and economic impacts to coastal communities. Here, management actions are examined that were taken by federal and state government agencies and responses of coastal residents to this extreme HAB event using a disaster risk management framework consisting of four phases: 1) prediction and early warning, 2) event response, 3) recovery and reconstruction, and 4) mitigation and prevention. Clear differences in management actions at the state level were evident in California, Oregon, and Washington during every phase, producing vastly different perceptions of management by coastal residents. A history of trusted relationships and coordination among agencies and with the fishing industry in Washington State was associated with more transparent and accepted management responses. The examination found that additional education, outreach, and trust-building exercises would provide benefits to communities affected by extreme HAB events. Our findings contribute to an understanding of climate change adaptation in coastal communities dependent on fishery resources.