The occurrence of organohalogen compounds in venous serum from post-partum mothers from two Argentinian cities, Salta and Ushuaia, has been investigated (n = 698). 4,4′-DDE was the most abundant compound in these cities, with geometric means of 33 and 67 ng/g lipid weight, respectively. City of residence, age and parity were the main determinants of the accumulation of these compounds. Hexachlorobenzene (HCB) was the second most abundant pollutant in Ushuaia, 8.7 ng/g lipid, and β-hexachlorocyclohexane (β-HCH) in Salta, 7.8 ng/g lipid. Decabromodiphenyl ether was higher in Ushuaia than Salta, 8.2 and 4.1 ng/g lipid, respectively. The predominance of β-HCH, 4,4′-DDE and 4,4′-DDT in Salta was related with higher use of pesticides for agricultural applications. The observed higher concentrations of 4,4′-DDE and 4,4′-DDT in the mothers from rural+semiurban sites than in urban areas were consistent with this agricultural origin. In addition, the most volatile organochlorine compounds included in this study, HCB and α-HCH, were mainly found in Ushuaia. The concentrations of the studied organohalogen pollutants in Argentina were lower than those found in other similar studies which is consistent with the location of these cities in the southern hemisphere. Age, mainly for 4,4′-DDE and polychlorobiphenyl (PCB) congeners 138, 153 and 180, and parity, mainly for HCB, β-HCH, 4,4′-DDT and PCB congener 118, were the second main determinants of the concentrations of these compounds. Gestational weight gain also influenced on the maternal levels of HCB, β-HCH, 4,4′-DDT and PCB congeners 118, 138 and 153. Higher weight accumulation during pregnancy involved dilution of these persistent pollutants. Body mass index (BMI) was a statistically significant determinant for 4,4′-DDT, α-HCH and PCB congeners 153 and 180. The observed direct correspondence between higher BMI and 4,4′-DDT concentrations was in agreement with the above reported inputs related with agricultural applications. The reverse correspondence of BMI with α-HCH and the PCB congeners indicated higher dilution at higher weight increase.