The main objective of this study was to analyze and evaluate the variation in the mass concentrations of PM2.5 ’s ionic and carbonaceous species in Hai Ba Trung District, Hanoi in winter of 2021 (from Jan. 5, 2021, to Jan. 29, 2021). In addition, this study also identified primary emission sources and factors affecting the variation of those species in PM2.5. The analytical result showed that the daily mean concentration of PM2.5 for the sampling period was 157,9 |!g/m3 - approximately 3 times higher than the limited value in QCVN 05:2013/BTNMT. Comparing daily average concentrations among major ionic and carbonous species, showed the concentration of OC was highest (30,8 |!g/m3), followed by SO42- (10,6 |!g/m3), NH4+ (4,1 |!g/m3), EC (2,4 |!g/m3), K+ (1,1 |!g/m3), and NO3- (0.02 |!g/m3) - lowest value, respectively. Other analytical results showed a very high correlation between SO42- and NH4+ (R2 = 0,98), indicating that these secondary species are likely to be formed by the oxidation of SO2 and NH3 originating from regional sources during long-range transportation to the sampling site. In contrast, NO3 - and EC were possibly emitted greatly from local traffic sources because of the oxidation of NOx, and incomplete combustion, respectively, while regional-scale biomass burning sources could be the main source of the significant amount of K+ and OC.