Chitosan and its modifications have received great attention over the past few decades due to its outstanding adsorption behavior toward various toxic heavy metals from aqueous solutions. In the review, the preparation strategies of modified chitosan (MCS) and its applications have been summarized. The effects of process variables (such as pH, temperature, adsorbent dosage, contact time, and co-existing ions), adsorption kinetics and isotherms, and adsorption mechanism were investigated. Moreover, the process parameters of heavy metal ions onto MCSs were optimized by response surface methodology. Finally, the regeneration of MCSs has been given considerable attention to evaluate their adsorption efficiency, and some dynamic adsorption studies were also discussed. The main objective of this review is to provide up-to-date information about the most important features of chitosan based adsorbents that may be helpful for synthesizing better adsorption property of modified chitosan and promoting its applications for heavy metal contaminate removal.