This study sought to assess the knowledge of consumers on the safety of vegetables produced in Morogoro Urban using Low Quality Water (LQW). The study determined how the knowledge of consumers influenced the perception and preference of various types of vegetables irrigated with LQW. A cross sectional study design was adopted and the 130 respondents were selected using simple random and purposive sampling techniques. Data collection was done using an interview schedule, focus group discussions and direct observation. Simple descriptive statistics, cross tabulations and chisquare test were used to analyse data. The study results indicated that, the vegetable consumers had knowledge that some vegetables in urban Morogoro were irrigated with LQW, but some of them were not sure if the vegetables they consumed were irrigated with LQW. Knowledge had a significant influence on the perception of consumers as it was revealed in this study that, consumers with knowledge that the vegetables were irrigated with LQW washed thoroughly and cooked the vegetables to maintain its safety. The study also found that five types of vegetables; Chinese cabbage, Amaranths, Pumpkin leaves, Sweet potato leaves and Okra were frequently bought and an average of 0.6kg was consumed at household per day. Sweet potato leaves were found to be the most preferred vegetables by respondents among the five types; consumers recognized it’s nutritious regardless of the kind of water used for irrigation. The study concluded that knowledge about the safety of vegetables had influence to the preference and perception of consumers. Based on the findings from this study, it is recommended that Morogoro Municipal Council through Morogoro Rural and Urban Water Supply Authority should set strategies of treating LQW frequently and the community should be assured on its safety before is allowed to use it. The community health officers should provide sanitary education to vegetable vendors and consumers. Also, extension agents should provide education to farmers on improved methods of irrigation.