Global population density and freshwater resources show uneven distribution patterns around the globe. This has forced farmers to use wastewater for the irrigation of food crops. Most industrialised nations purify their wastewater before using it to irrigate crops for food, fibre and other uses. This practice presents both positive and negative effects with respect to agricultural use, as well as in the context of environmental contamination and toxicology. This chapter highlights the harmful and beneficial impacts of wastewater irrigation. Cu, Cr, Mn, Fe, Pb, Zn and Ni are some of the harmful metals found in it. Treated wastewater reuse has been expanding at a rate of between 10% and 29% annually in Europe, the United States and China, and as much as 41% in Australia. The chemical pollutants found in untreated wastewater may be rather diverse and include substances such as fertilisers, heavy metals, textiles, leather, paper, sewage, food processing waste, pesticides and chemical waste from industrial effluent The direct use of wastewater for irrigation has serious health consequences. This chapter also highlights the irrigation water criteria, list of parameters and methods adopted for analysis of water quality and sampling methods of water for analysis. This chapter also highlights the Private/Government laboratories, institutes and organisations which provide financial and technical support to universities and research institutes for collaborative research like Pakistan Council of Research in Water Resources, Pakistan Environmental Protection Agency, Institute of Soil and Environmental Sciences, University of Agriculture Faisalabad, Pakistan, Centre of Excellence in Analytical Chemistry, University of Sindh, Jamshoro, Pakistan, Institute of Environmental Studies, University of Karachi, Department of Soil and Environmental Science, University of Peshawar, Peshawar and IWMI. In order to fulfil the criteria for irrigation water quality and to guarantee the safety of crops and the environment, it is necessary to treat wastewater in order to eliminate pollutants including pathogens, organic materials, nutrients and trace elements. This chapter delves into the several treatment procedures, including physical, chemical and biological approaches, and highlights how successful they are in creating irrigation-quality water. It goes on to discuss how treated wastewater may improve soil fertility, increase agricultural production in areas with water scarcity and decrease the demand for freshwater. All things considered, a sustainable method of managing water resources is to use treated wastewater for irrigation. This helps with both water conservation and the sustainability of agricultural practices.