The medicine, personal care products, and cleaning supplies that we use on a daily basis constitute a unique class of environmental pollutants termed “contaminants of emerging concern” (CECs). When excreted or washed away, these compounds enter wastewater treatment plants (WWTPs) but are not specifically targeted for removal. As a result, WWTP effluent introduces kg/day loads of mixtures of emerging contaminants into receiving urban estuaries and waterways, and leads to subsequent bioaccumulation in aquatic wildlife. Researchers are now focused on determining what effects these mixtures of contaminants may have on fish and other aquatic biota. Because many CECs are known to elicit mitochondrial toxicity in the laboratory, the recent study by Yeh et al. investigated whether exposure to mixtures of CECs results in liver mitochondrial dysfunction in fish. We focused on juvenile Chinook salmon (Oncorhynchus tshawytscha), a critically-endangered species here in the Pacific Northwest whose early life history includes a month-long residency in WWTP effluent-impacted waters. The fish were exposed in the laboratory to a diet dosed with a mixture of 16 of the predominant CECs detected in a previous field study of three Puget Sound urban estuaries (Meador et al., 2016). Elevated respiratory activity per liver mitochondria, mitochondrial oxidative injury, and mitochondrial metabolic changes resulted from dietary exposure to the contaminant mixture. An elevation of state 4 (proton leak) respiration suggested reduced efficiency of oxidative phosphorylation. Field-collected fish exposed to CECs showed similar but less severe trends in mitochondrial metabolism. Our results indicate that exposure to environmentally-relevant mixtures of CECs does indeed affect mitochondrial function in fish, and support analysis of mitochondrial function as an indicator of the sublethal effects of CECs in wild fish.