As infectious diseases continue to be one of the greatest health challenges worldwide, the demand toward alternative agents is continuously increasing. Recent advancement in nanotechnology has expanded our ability to design and construct nanomaterials to treat bacterial infections. Carbon nanotubes are one among these nanomaterials. Herein, we describe the covalent functionalization of the single-walled carbon nanotubes (SWCNTs) with multiple molecules of ciprofloxacin. The prepared nanoantibiotics were characterized using different techniques, including transmission electron microscopy, Raman spectroscopy, and thermogravimetric analysis. The characterization of the nanoantibiotics confirmed the successful covalent functionalization of the SWCNTs with 55% of functionalization as has been observed by thermogravimetric analysis. The release profile revealed that 90% of the loaded ciprofloxacin was released within 2.5 h at pH 7.4 showing a first-order release profile with R2>.0.99. Interestingly, the results of the antibacterial activity indicated that the functionalized SWCNTs have significant increase in the antibacterial activity against the three strains of bacteria by 16-fold for Staphylococcus aureus and Pseudomonas aeruginosa and by 8-fold for Escherichia coli in comparison to the ciprofloxacin free drug. Moreover, the synthesized nanoantibiotic showed high hemocompatibility and cytocompatibility over a wide concentration range. © 2017 Assali et al.