We investigated testosterone production and semen parameters in farmed Arctic foxes by dietary exposure to persistent organic pollutants (POPs) for 22 months. Eight male foxes were given a diet of POP-contaminated minke whale blubber, whereas their eight male siblings were fed a control diet containing pig fat as the main fat source. The minke whale-based feed contained a ∑POPs concentration of 802 ng/g ww, whereas the pig-based feed contained ∑POPs of 24 ng/g ww. At the end of the experiment, ∑POP concentrations in adipose tissue were 8856 ± 2535 ng/g ww in the exposed foxes and 1264 ± 539 ng/g ww in the control foxes. The exposed group had 45-64% significantly lower testosterone concentrations during their peak mating season compared to the controls (p ≤ 0.05), while the number of dead and defect sperm cells was 27% (p = 0.07) and 15% (p = 0.33) higher in the exposed group. Similar effects during the mating season in wild Arctic foxes may affect mating behavior and reproductive success. On the basis of these results, we recommend testosterone as a sensitive biomarker of POP exposure and that seasonal patterns are investigated when interpreting putative endocrine disruption in Arctic wildlife with potential population-level effects.