Continuous measurements of black carbon (BC) aerosol were made at a midsized urban site in Baoji, China, in 2015. The daily average mass concentrations of BC varied from 0.6 to 11.5 µg m–3, with an annual mean value of 2.9 ± 1.7 µg m–3. The monthly variation indicated that the largest loading of BC occurred in January and the lowest in June. The mass concentrations of BC exhibited strong seasonality, with the highest occurring in winter and the lowest in summer. The large BC loadings in winter were attributed to the increased use of fuel for domestic heating and stagnant meteorological conditions, whereas the low BC levels in summer were related to the increases in precipitation. BC values exhibited similar bimodal diurnal patterns during the four seasons, with peaks occurring in the morning and evening rush hours and an afternoon trough, which was associated with local anthropogenic activities and meteorological conditions. A potential source contribution function model indicated that the effects of regional transport mostly occurred in spring and winter. The most likely regional sources for BC in Baoji were southern Shaanxi province, northwestern Hubei province, and northern Chongqing during spring, whereas the northeastern Sichuan Basin was the most important source region of BC during winter.