This study assesses the contribution of informal economic activities towards environmental degradation in Mwanza City. The specific objectives were (i) to determine the extent to which the informal economic activities have affected the physical and social environment (ii) to find out the awareness of the informal economic vendors in as far as their activities contributing to degrade the environment is concerned (iii) to examine challenges that are associated with environmental degradation. The study was carried out using Descriptive research design; it involved 68 respondents from six vending centres in the two municipalities that constitute Mwanza City. The sample was selected by using systematic random sampling after having been computed using Morgans’s formular of Chi – Square. The study employed a triangulation approach, mixing quantitative and qualitative elements. The triangulation was applied at the methodological level and at data collection techniques. Therefore questionnaires and interviews were used to obtain the data for the study. However tables, pie charts, bar graphs, were used to present the finding. But also verbatim and direct quotations from the interviews were presented. Findings revealed that informal economic activities have contributed enormously in as far degradation of the environment is concerned. This has been realised in the measures that were applied to test the degradation such as sanitational status of the place, the ordour of the place, including its length, frequency and its offensiveness character. Also the loss of greenery and natural environment was tested and so much more. The findings from all these indicated that the environment has been much degraded. xv It was also found that the vendors are aware of environmental degradation and its causes only that it was due to negligence and lacking the spirit of being responsible that escalated the problem.