<p>N-nitrosodiphenylamine (N-NDPHA) is a highly soluble, toxic disinfection by-product in water. Even at low concentrations, long-term exposure to N-NDPHA can lead to a variety of health consequences. As a result, removing N-NDPHA from aqueous samples using an efficient and cost-effective adsorbent is highly required. Polyhexahydrotriazine (PHT-1) has been reported to exhibit thermal and chemical stability, as well as recyclability. Hence, in this work, PHT-1 was prepared using a one-pot facile synthesis, characterized, and investigated for the removal of N-NDPHA from aqueous solutions. The impacts of solution pH, contact duration, adsorbent dose, and adsorbate concentration were studied. Using 0.2g L⁻¹ of PHT-1 adsorbent at pH 6, a remarkable removal efficiency of 85% for N-NDPHA from wastewater solution was obtained. At room temperature, PHT-1’s maximum adsorption capacity was obtained to be 33.61 mg g⁻¹. The adsorption kinetics and isotherm followed pseudo-second-order kinetics and fitted well with both the Langmuir and Temkin models. According to the thermodynamic characteristics, the chemical adsorption process is predominant, especially at low concentrations of N-NDPHA, and the adsorption of N-NDPHA onto PHT-1 adsorbent is favorable and endothermic. According to this study, PHT-1 adsorbent can be easily regenerated and used at least three times before its removal effectiveness starts to decline.</p>