Nanozerovalent iron (nZVI), due to its high activity toward persistent organic contaminant degradation and heavy metal removal, has attracted applications in industrial wastewater treatment as well as in situ soil remediation techniques. This chapter discusses the emergence of nanoscale hybridization of nZVI-based materials, their multifunctional capabilities, and their importance in environmental remediation and water treatment. It provides a brief review on the environmental fate and toxicity concerns from nZVI- based materials. The chapter then discusses the complexity in assessing environmental risk of nZVI-based Nanohybrids (NHs) from their altered and emergent properties. The efficacy of practically applying nZVIs and their NHs in wastewater treatment and groundwater remediation depends on their aggregation behavior in aquatic media and transport properties through porous media. Due to their high van der Waals (vdW) and magnetic attraction forces, nZVI tends to aggregate fast and, therefore, also can get filtered out losing the delivery efficiency for groundwater injection wells.