The aim of this study was to assess faecal bacterial contamination in tilapia fish from wastewater treatment ponds at Mzumbe and in pristine water in Mindu dam. Tilapia fish (fish flesh and fish intestines) and water samples were analysed for Escherichia coli and total plate count. The concentration of E. coli in fish intestines ranged from about 1 - 3.5 log cfu/g and <1 log cfu/g in fish flesh. Total plate count ranged from 1 – 3 log cfu/g in fish flesh and 2 – 6 log cfu/g in fish intestines. The concentration of E. coli in pristine water in Mindu dam ranged from 0 to 15 cfu/mL. From the inlet to outlet of Mzumbe wastewater treatment pond, there was a significant reduction (p<0.05) of E. coli concentration along the gradient from 2.05 to 0.55 log cfu/mL, respectively. These findings demonstrated that tilapia fish from the two study sites were of good quality for human consumption based on microbial faecal contamination. On the other hand treated wastewater of the quality found in this study may be used for aquaculture. However, continuous monitoring for bacteriological quality and safety parameters including E. coli and total plate count is required.