In this study, we used electrospun polycaprolactone (PCL) or a mixture of PCL and gelatin (Gel) in a mixed acidic solvent to develop antimicrobial electrospun nanofibers. Carboxyl-modified mesoporous silica nanoparticles (CMSNs) or CMSNs loaded with antibiotic drugs polymyxin B and vancomycin (CMSNs/ABs) were mixed with the electrospinning solution in concentrations of 1%, 2.5% and 5%. The nanofibers diameter measured between 122 and138 nm. Higher concentrations of gelatin or CMSNs increased hydrophilicity and degradability of the nanofibers. CMSNs enhanced nanofibers mechanical strength. PCL/Gel nanofibers incorporated with CMSNs/ABs (2.5% and 5%) showed high antibacterial efficiency against Pseudomonas aeruginosa and Staphylococcus aureus. Also bacterial cell adhesion decreased when 2.5% and 5% of CMSNs/ABs were incorporated in PCL/Gel mats. MTT and hemolysis assays indicated excellent biocompatibility of all types of electrospun nanofibers. This study confirms that a proper mixture of PCL, gelatin and CMSNs loaded with two antibiotics could offer antimicrobial activities with high biocompatibility and biodegradability properties. [GRAPHICS] .