The present study reports unique data on concentrations of several classes of organochlorine pesticides and polychlorinated biphenyls in blubber biopsies from healthy living fin whales (Balaenoptera physalus) from the Gulf of California, Mexico, one of the most isolated and unstudied population in the world. OC levels in this population were generally lower than levels reported in fin whales from other regions. The rank order of OCs were ∑DDTs (range from 300 to 2400 ng g−1 lw) > ∑PCBs (range from 40 to 290 ng g−1 lw) > ∑HCHs (range from <LOQ to 92 ng g−1 lw) ≥ ∑CHLORs (from < LOQ to 100 ng g−1 lw). The most abundant OC pesticide measured was the DDT metabolite, p,p′-DDE. The PCBs 138, 153, and 180 were the most abundant PCBs congeners found in the fin whales samples. Males had significant higher concentrations of ∑OC, ∑DDTs and ∑PCBs than females (P < 0.05), although the p,p′-DDE/∑DDTs ratios were similar between the sexes. Although the OC concentrations found in this population were generally below the levels that would be expected to cause deleterious health effects, the maximum values observed (2700 ng g−1 lw) in some animals were higher than those associated with reproductive effects in whales. Given the small population size and highly isolated characteristics of Gulf of California fin whales, health effects in individuals could readily translate into population-level effects. Future research on this topic will be necessary to better understand the role that these compounds may have on the health of this population. © 2009 Wiley Periodicals, Inc. Environ Toxicol 25: 381–390, 2010.