Street vending of hand-filled sachet drinking water is common, but not regulated in Malawi. There are concerns that sachet drinking water may be at risk of contamination due to unhygienic handling and/or unsafe sources. From 76 sachet vendors currently operating in Mzanza, 76 interior sachet water samples, 76 exterior bag rinse samples and 70 source water samples were analyzed for Escherichia coli (EC) and total coliforms (TC). All vendors use boreholes and taps for packaging operations and most (74%) do not treat their water. 50% and 20% of source water samples were positive (CFU/100ml≥1) for TC and EC, respectively. At the point-of-sale, most interior water samples contained at least 1 CFU/100ml for both TC (96%) and EC (64%) while 99% and 74% of exterior bag rinse samples were positive (CFU/100ml≥1) for TC and EC, respectively. The results indicate that contamination of sachet water in Mwanza increases from source to point-of-sale, possibly due to unhygienic handling.