Being aware of the potential health effects brought on by exposure to radionuclides, besides chemical and air pollution, produced by coal-fired brick kilns, first-ever measurements of terrestrial radionuclides were performed in the topsoil sampled from the surrounding of a randomly chosen coal-fired brick kiln operating at the outskirts of megacity Dhaka, Bangladesh. By employing the HPGe gamma-ray spectroscopy, the activity concentrations of 226Ra, 232Th, and 4 K was found to be in the range of (19.2 ± 2.7–54 ± 7.0) Bq/kg, (33 ± 5.3–68 ± 9.5) Bq/kg, and (360 ± 43–540 ± 65) Bq/kg respectively, where almost all the values of 40 K, 232Th; and some of the values of 226Ra exceeded the corresponding world average values. Possible causes of the elevated level of radionuclides include the deposition of bottom ash in lowlands, the accumulation of fly ash in soils, and the fallout of fine particles that absorb the minerals released from the coal burning process. 137Cs was also found in two samples that might indicate contamination of the feed coal. Most of the outdoor absorbed dose rates, some internal absorbed dose rates, annual effective dose, gamma level index and excess lifetime cancer risk surpass the worldwide average. According to these hazard parameters, there are health risks to the brick kiln workers and the populace who consumes food crops produced in the studied agricultural soils. The present quantitative measurements urge the municipal authorities to manage and monitor the discharge of fly ash from the brick kilns and take precautionary actions to reduce unwanted health hazards. It also demands to monitor of the human health of workers and residents near the brick kilns.