Due to their unique physical and chemical characteristics, carbon-based nanomaterials have a high potential for use in biomedical studies. However, their interaction with blood components, particularly red blood cells (RBCs), is of concern due to potential hemolytic activity. Certain studies have demonstrated no clear risks, while others have indicated that carbon-based nanomaterials may pose health threats. The current study aimed to explore the hemolytic properties of selected carbon nanostructures characterized by distinct morphologies and surface functionalities. The examined nanomaterials included graphene oxide (GO), reduced graphene oxide (rGO), multi-walled carbon nanotubes (MWNTs), and high-purity short-walled carbon nanotubes (HPS), as well as their hydroxylated derivatives (HPS-OH and MWNT-OH). The objective was to investigate how their features affect blood compatibility and their potential toxic effects. Hemolysis assays were conducted on feline red blood cells at different concentrations, along with zeta potential, UV-Vis spectrometry, NTA, BSA adsorption, and scanning electron microscopy (SEM) analyses. Additionally, microscopic assessment of erythrocyte morphology provided visual confirmation of nanomaterial-induced alterations in cell integrity and aggregation behavior. Results show that the hemolytic activity of the studied carbon nanomaterials is dependent on their concentration, surface chemistry, charge, and aggregation properties. Understanding these relationships is important for predicting the biocompatibility of nanomaterials and guiding the safe design of carbon-containing nanostructures developed for biomedical and engineering applications.