This article describes the selective and sensitive determination of mefenamic acid on single walled carbon nanotubes modified glassy carbon electrode (GCE) employing square wave voltammetry for the first time. The developed sensor exhibited amelioration in the peak current response with a negative shift in the peak potential in comparison to multi walled carbon nanotubes modified GCE and bare GCE. A good linear relationship has been found between the anodic peak current and mefenamic acid concentration in the range of 0.1-35 mu M with limits of quantification and detection as 44.7 and 13.4 nM, respectively. The interfering effects of the commonly existing metabolites in the biological fluids have been investigated on the current response of the drug. The developed sensor was successfully applied for the assay of mefenamic acid in pharmaceutical formulations. Furthermore, the applicability of the proposed method to determine mefenamic acid in human urine samples obtained from healthy volunteer and patient after 4 h of administration of the drug is illustrated.