This paper is a study of the radiological impact of a coal-fired power plant in Spain. Activity concentrations of six natural radionuclides were determined in coal, ash, mine wastes and sediments by gamma-ray spectrometry. The average activity concentrations of ²³⁸U, ²²⁶Ra, ²²⁴Ra, ²¹⁰Pb, ²³²Th and ⁴⁰K in coal were 24, 30, 28, 41, 23 and 242 Bq kg⁻¹ and in ash were 103, 128, 101, 124, 88 and 860 Bq kg⁻¹, respectively. The enrichment factor, radium equivalent activity and alpha index in the ash sample have been estimated. For the five waste pile samples, the absorbed dose rate was higher than the world average dose rate (60 nGy h⁻¹). The dependence of radionuclide concentration on the grain size of nine sediments was also studied. The analysis of the radionuclides in waste and sediment samples will demonstrate the distribution and mobility of these elements through the environment, where a potential risk of contamination can be detected.