Previous studies have found relatively high chlorinated paraffin (CP) concentrations in moose (Alces alces) compared with other wildlife from Scandinavia. To explore CP accumulation behaviors in this long-lived terrestrial mammal, temporal trends of muscle concentrations of CPs were first measured in samples collected over the past 40 years from moose calves from Grimsö, Sweden. The four CP classes, i.e., very-short-chain, short-chain, medium-chain, and long-chain (LCCPs) classes, showed similar temporal trends, with increasing concentrations from 1982 to the 1990s, relatively high levels in two time periods around 1993 and 2008, and decreasing concentrations after 2012. A concentration plateau period was identified, and moose samples of both sexes and different ages from the median year (1993) of the concentration plateau period were selected for further analysis. CP levels increased exponentially with age in the male moose, while CP levels were found to exponentially decrease with age in females. LCCPs showed the slowest decreasing tendency with age in females compared with the other three classes, resulting in a general increase of the LCCP proportions with age. The sex-biased accumulation of CPs indicates additional stresses from these POP-like chemicals toward males of the largest and one of the most widespread terrestrial mammals in northern hemisphere forests.