The Adenoviridae and Polyomaviridae families comprise a wide diversity of viruses which may be excreted for long periods in feces or urine. In this study, a preliminary analysis of the prevalence in the environment and the potential usefulness as source-tracking tools of human and animal adenoviruses and polyomaviruses has been developed. Molecular assays based on PCR specifically targeting human adenoviruses (HAdV), porcine adenoviruses (PAdV), bovine adenoviruses (BAdV), and bovine polyomaviruses (BPyV) were applied to environmental samples including urban sewage, slaughterhouse, and river water samples. PAdV and BPyV were detected in a very high percentage of samples potentially affected by either porcine or bovine fecal contamination, respectively. However, BAdV were detected in only one sample, showing a lower prevalence than BPyV in the wastewater samples analyzed. The 22 slaughterhouse samples with fecal contamination of animal origin showed negative results for the presence of HAdV. The river water samples analyzed were positive for the presence of both human and animal adenoviruses and polyomaviruses, indicating the existence of diverse sources of contamination. The identities of the viruses detected were confirmed by analyses of the amplified sequences. All BPyV isolates showed a 97% similarity in nucleotide sequences. This is the first time that PAdV5, BAdV6, and BPyV have been reported to occur in environmental samples. Human and porcine adenoviruses and human and bovine polyomaviruses are proposed as tools for evaluating the presence of viral contamination and for tracking the origin of fecal/urine contamination in environmental samples.