<p><span style="color: rgb(34, 34, 34); font-family: Merriweather, serif; font-size: 18px;">Composite electrospun nanofibers based on polycaprolactone (PCL) have shown promise in various biomedical applications due to their unique properties. This study investigates the effects of incorporating hydroxyl (–OH)- or carboxylic acid (–COOH)-functionalized multiwall carbon nanotubes (MWCNTs) into PCL matrices. Two types of functionalized additives, MWCNT-OH and MWCNT-COOH, were used at different concentrations (0.06 and 0.12&nbsp;wt%). Various characterization techniques including FTIR, XRD, AFM, SEM, water contact angle analysis, and tensile strength testing were employed to evaluate changes in nanofiber morphology, crystallinity, surface topography, wettability, and mechanical properties. In addition, in vitro cytotoxicity assays were conducted using HUVECs and L929 fibroblasts over 1-, 3-, and 5-day intervals. This study represents a novel examination of (–OH)- and (–COOH)-functionalized MWCNTs as additives in electrospun PCL biopolymer matrices. The findings indicate that incorporating small amounts of (–OH)- or (–COOH)-functionalized MWCNTs enhances the physicochemical characteristics of PCL nanofibers, making them more suitable for biomedical applications. While both types of functionalized MWCNT additives improved properties compared to pure PCL nanofibers, (–COOH)-functionalized MWCNT-incorporated nanofibers exhibited the most favorable features. In conclusion, this research highlights the potential of tailored PCL-based composite nanofibers containing functionalized MWCNTs as advanced biomaterial systems for biomedical applications, contributing to the development of innovative biomaterials for diverse biomedical contexts.</span><br></p>