The advancement of adequate wastewater treatment (WWT) technologies and adopting circular economic principles have thus gained paramount importance. WWT is a crucial component of water quality management strategies in cold climates. In light of the limitations associated with chemical treatment methods, there has been a shift towards biological treatment processes to alleviate adverse conditions in natural water systems in cold climates. Utilizing microbes for WWT and subsequently discharging the treated water into natural bodies is an optimal approach for environmental preservation in regions with very low temperatures. Fungal microbes are particularly advantageous in remediation process due to their cost-effectiveness, rapid growth, ease of cultivation, and environmentally friendly characteristics. The immobilization of fungi allows for repeated treatment system use, presenting significant benefits for several applications. Self-assembled fungal pellets demonstrate considerable potential in WWT, as they can be easily separated from dye-laden wastewater while exhibiting effective decolorization capabilities and robust tolerance to varying pH levels during both cultivation and adsorption processes in cold climate regions. The current chapter briefly uncovers the WWT and its type in the initial sections. The subsequent section has emphasized the diverse species of fungi inhabiting cold climates and their probable applications, adaptations, and limitations in such climates for WWT.