Many environmental factors can stress and cause the mortality of reef-building corals with elevated thermal conditions predominant. The historically early explanation for the absence of coral reefs in the eastern Pacific region—“cold ocean currents and upwelling”—does account for some degree of coral bleaching and mortality but is superseded by region-wide mass mortality caused by El Niño warming events that in recent years are superimposed on increasing global warming. Major eastern Pacific reef-building coral species are highly tolerant of prolonged low salinity conditions and have even demonstrated modest reef development in an estuarine environment. Extreme midday low tidal events in the dry season and during La Niña events result in shallow reef zone coral exposure, bleaching, and mortality. Recovery from these disturbances occurs in <10 years. Tropical cyclones take place at Mexico’s latitude, and seismic events in the equatorial eastern Pacific, generally causing only local and minor damage to coral reefs. Ocean acidification in the Galápagos Islands has minimized internal cementation and lowered coral skeletal development. A high incidence of lesions and skeletal abnormalities is observed in corals in some areas, but no confirmed disease outbreaks have been reported.