We first report a single-light-source orthogonally pumped triaxial atomic magnetometer with a double-cell structure. By using a beam splitter to equally allocate the pump beam, the proposed triaxial atomic magnetometer is responsive to magnetic fields in all three directions, and without sacrificing system sensitivity. The experimental results indicate that, the magnetometer achieves a sensitivity of 22 fT/Hz1/2 in x-direction with a 3-dB bandwidth of 22 Hz, a sensitivity of 23 fT/Hz1/2 in y-direction with a 3-dB bandwidth of 23 Hz, and a sensitivity of 21 fT/Hz1/2 in z-direction with a 3-dB bandwidth of 25 Hz. This magnetometer is useful for the applications that require the measurements of the three components of the magnetic field.