<p>The linear and branched polyethyleneimine (PEI)-based materials have shown their potential applications in various fields including water purification technologies. Due to several primary, secondary, and tertiary amine groups in their structure, PEIs as such and PEI-based copolymers, hybrid materials, and nanocomposites are capable of entrapment or adsorption of contaminants from different categories such as dyes, heavy metal ions, pharmaceuticals, and oils. The latest interesting reports in the literature about PEIs-based materials have proved the continued interest and significant advancements in these materials for developing new and highly efficient adsorbents. This review provides important basic information about PEI and its structure, a glimpse of its various applications, and, collective information with an analysis of the latest works on PEI-based materials developed to be used as adsorbents for the adsorption removal of pollutants from water. The latest advancements are discussed with the main results while the interesting data about types of materials developed, pH, adsorption time, etc. is reported in tabular format. The report concludes with the study’s main findings and future prospectus regarding synthetic polymer chemistry challenges in PEIs and PEI-based materials.</p> Graphical abstract <p>Schematic representation of the adsorption of various pollutants onto linear and branched polyethylenimine (PEI). </p>