Thirty-five polybrominated diphenyl ethers (PBDEs) and eight other alternative flame retardants were measured in air samples (vapor plus particles) collected at six sites near the North American Great Lakes between 2005 and 2019 as part of the Integrated Atmospheric Deposition Network (IADN). These data were analyzed using a multiple linear regression model to determine spatial and temporal trends. Overall, the levels of flame retardants remain significantly higher in urban sites compared to rural and remote sites except for pentabromoethylbenzene (PBEB), hexabromobenzene (HBB), and total Dechlorane Plus (ΣDP). Here, we report the first findings of decreasing levels of ΣDP at Sturgeon Point, New York. The atmospheric levels of total PBDEs remain unchanged over time near Lakes Michigan and Superior and declined near Lakes Erie and Ontario, with rate constants at the latter two lakes revealing halving times of approximately 7 to 14 years. This work presents results from the first investigation of PBDE source apportionment in the Great Lakes atmosphere. Source apportionment by use of positive matrix factorization (PMF) identified two legacy commercial technical mixtures (i.e., penta-BDE and deca-BDE mixes) and elucidated a factor representing ambient degradation. Our results show that weathered local sources of technical commercial mixtures, and their photolysis contribute most to the total PBDE burden in the Great Lakes atmosphere.