The biological properties of water samples collected from six different open wells belonging to Thannyam Grama panchayat in Thrissur district have been analyzed to assess its quality and potability. Water sample collection and analysis were carried out during the pre-monsoon period of March-May 2016. Different bacteriological parameters such as total coliform count, faecal coliform count and Escherichia coli count and algal parameters such as presence or absence of algal indicators of water pollution, pollution index of algal genus, pollution index of algal species and pollution index score were determined for the selected well water samples. The results obtained have been compared with IS: 10500 specifications for drinking water to assess the quality and suitability. The investigation revealed gross pollution of studied open well water sources either due to excess levels of chemical parameters indicated by the detection of algal indicators of water pollution or due to fecal contamination based on the detection of bacterial indicators or due to both. The various factors such as improper waste disposal, dumping of solid wastes, leakages from septic tank and contamination due to fecal matters of animals and birds may be the reasons. The investigation concludes that all the open well water sources selected for the study are unfit for human consumption and requires immediate attention and urgent treatment before being used up for drinking and other domestic purposes.