High concentrations of heavy metals in urban watersheds can offer harmful effects to human health and have contributed to environmental contamination. The present work aims to evaluate the total concentration of Zn (zinc), Mg (magnesium), lead (Pb), Cr (chromium), manganese (Mn) and Ni (nickel) analyzed according to FAAS—Flame Atomic Absorption Spectrometry, in samples of the aquatic macrophyte Egeria densa present in the urban stretch of the Cascavel River watershed, Guarapuava, PR; and specific objectives to identify the potential sources of contamination by heavy metals and to obtain physical parameters of the water. The elements zinc, magnesium, manganese and lead showed higher potential emissions upstream, a fact associated with the proximity of the industrial zone of Guarapuava. It is likely that the increase in electrical conductivity values at the upstream points is related to the discharge of domestic effluents. The decrease of conductivity and total dissolved solids in the sample points occurs downstream, corresponding to the lower topography of the study area and the end of the urban stretch of the Cascavel River basin. Despite the concentrations of heavy metals being considered critical, the plant showed efficiency in bioaccumulation of these chemical elements, being an effective tool for research and environmental assessment, and aquatic macrophytes can be the basis for biomonitoring studies of urban environments impacted by heavy metals.