Nanofiber mats of polyvinyl(pyrrolidone) (PVP) with Garcinia mangostana extract (GME) as the encapsulated drug have been developed using electrospinning. SEM images of all electrospun PVP/GME composite nanofiber mats showed that they had similar and smooth morphology, no beads, and spindle shape. Its average diameter decreased and its surface area therefore increased with the decrease of its PVP concentration. The benefit of high surface area is obvious in drug delivery systems for poorly water-soluble drugs. Their FTIR spectra indicated that PVP and GME interacted intermolecularly via hydrogen bonds in the composite nanofiber mats. A conformational change in the C-H chain of PVP occurred in the composite nanofiber mats due to the intermolecular interactions. Their XRD patterns confirmed that they were amorphous because of amorphization during electrospinning. The XRD analyses also strengthened the FTIR studies; namely, GME and PVP formed intermolecular interactions in the electrospun composite nanofiber mats. As a result, GME as the encapsulated drug was molecularly dispersed in the electrospun PVP nanofiber matrix that functioned as a drug delivery system. From the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, the composite nanofiber mats exhibited very high antioxidant activities despite having been exposed to high voltage during electrospinning. Therefore, they are potential antioxidant products for food and pharmaceutics.