Diluted bitumen (dilbit) from Canada’s oil sands is toxic to early life stages of fish, including Pacific salmon that are at an increased risk of exposure from pipeline spills. For my Master’s thesis, I exposed coho salmon (Oncorhynchus kisutch) embryos to very low, environmentally relevant concentrations of the water-soluble fraction of dilbit (WSFd) at ambient temperature or at ambient + 3oC (heated), to address a key uncertainty about how environmental temperature influences the toxic response in these fish. I showed that elevated temperatures exacerbate organismal endpoints of dilbit toxicity, like mortality rates, growth and cardiorespiratory performance, immediately following exposures, and increase latent toxic effects in older life stages. This has implications for the large-scale impacts of oil spills for vulnerable fish populations as water temperatures continue to increase with climate change.