The objective of this study was to assess the roles of labour union in preventingrnenvironmental pollution, a case study of Labour unions of Modjo and East Africa tanneriesrnin Modjo Town, and the working relationship with stakeholders that deal with thernenvironment. Mixed methods research was applied by using qualitative and quantitativernapproaches to the stated objective. The survey questionnaire and interview checklistsrnprepared as a research tool to collect data from 110 the respondents and key informantsrninterview. The data were analyzed using descriptive statistics such as frequency, tables,rnpercentages, and mean scale, to show the extent to which the respondents agreed or disagreedrnwith the statements in the questionnaire, using a 5-points Likert scale. The result shows, thatrnthe involvement of labor unions in environmental pollution prevention is not adequatelyrnutilized, poor cooperation with stakeholders and there are non-compliance of the tanneriesrnstudied with some of the environmental regulations and standards that resulted in therndownstream user communities of Modjo River, affected by the polluted wastewaterrndischarged. Following community grievances, the landfill in-use by the tanneries and ModjornMunicipality was prohibited and closed in 2018, but without rehabilitation. Therefore, duernattention is required to enhance labour unionsâ€™ role and participation through training andrnawareness creation to enable reduce or prevent environmental pollution, attain secured jobsrnfor the workers in the tanneries and institutional capacity building at different governmentrnlevels and more collaboration of relevant stakeholders with the labour unions to contributernmore to sustainable development.