Herein, β-Ga2O3 photocatalyst was designed to improve the photocatalytic activity. Therefore, two strategies were employed: chemical modification by Ce doping and morphological control by formation of nanofibers. Therefore, Ce-doped β-Ga2O3 nanofibers were successfully synthesized using a sol–gel derived electrospinning. These synthesized nanofibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV–vis spectroscopy. The SEM and XRD results indicated that Ce doping slightly influence on the morphology and crystal structure of nanofibers. In addition, the UV–vis transmittance spectra result indicates that the bandgap energy of Ce-doped β-Ga2O3 nanofibers was significantly reduced from 4.92 eV to 4.54 eV. In specific, the 0.7 mol % Ce-doped β-Ga2O3 nanofibers exhibits the lowest optical band gap energy as 4.54 eV. Moreover, the photodegradation properties of β-Ga2O3 nanofibers were evaluated by using the Methylene Blue (MB) under UV light. Interestingly, the β-Ga2O3 nanofibers doped by 0.7 mol% cerium atom exhibited the highest photocatalytic activity than other synthesized nanofibers. Consequently, from the overall characterizations, it was found that improved activity of photocatalytic degradation will be attributed to the narrow optical bandgap energy and reduced recombination rate arising from the cerium doping.