Bivalve mollusks, such as mussels, are bioindicators used to monitor environmental health due to their filter-feeding behavior, which allows them to accumulate contaminants from water. In this study, we focused on one mussel species, Mytella strigata, which has been reported as invasive in the Philippines. We investigated both the densities of M. strigata and the occurrence of Escherichia coli and coliform bacteria in samples collected from Tangub, Misamis Occidental, and Baroy, Lanao Del Norte, Philippines. Mussels larger than 40 mm were randomly gathered, cleaned, and measured for shell length and weight, and their meat was carefully extracted and sealed for subsequent analysis in a controlled laboratory setting. The densities of M. strigata in Tangub City and Baroy were 2333 ind/m2 and 2100 ind/m2, respectively. A higher Most Probable Number (MPN) was found in Baroy compared to Tangub for both E. coli (>1600/100 g) and coliform counts (>1600/100 g) and results were statistically significant for E. coli counts based on t-test (p<0.05). As M. strigata mussel is an edible species, these results are therefore useful for wastewater treatment measures, ensuring the safety and hygiene of shellfish.