In this study, we examined activated and non-activated carbon nanoparticles (CNPs) derived from oil palm empty fruit bunch (OPEFB) fibers for their nanomaterial characteristics and their potential effectiveness in heavy metal removal. To investigate these properties, transmission electron microscopy, scanning electron microscopy (SEM), EDX, Fourier transform infrared spectroscopy, particle size analysis, X-ray diffraction, and atomic absorption spectrophotometry were employed. This study shows that both the activated and the non-activated CNPs were in the form of well-dispersed and aggregated particles. As analyzed using SEM, the external surfaces of the non-activated CNPs were determined to be irregular, while those of the activated CNPs had a more circular shape without aggregation. Carbon was the most dominant element observed in these CNPs, and the occurrence of its activation process altered the chemical functional groups of the non-activated CNPs by shifting their wavenumbers and intensities. Additionally, the activation process increased the crystallinity domain in the activated CNPs. OPEFB fibers could be valorized to obtain both activated and non-activated CNPs that had the potential efficiency to remove heavy metals, including copper (Cu), lead (Pb), iron (Fe), and zinc (Zn) at certain times. Based on the analysis of the Langmuir and Freundlich models, the activated and non-activated CNPs were found to have shown favorable adsorption to Cu, Pb, and Fe, with a percentage of heavy metal removal of over 84%. The adsorption of heavy metals was carried out via a chemical process.