We demonstrated on a synchronously pumped femtosecond optical parametric oscillator with dual-signal-wavelength operation. Our results showed that the dual-wavelength oscillation is not determined by the net-zero dispersion but rather by the balance of phase matching and group-velocity mismatching caused by the nonlinear crystal between the two signals. With a MgO-doped periodically poled lithium niobate as the nonlinear crystal, total signal power up to 530 mW was obtained by using a 2.6 W femtosecond Ti:sapphire laser at the central wavelength of 808 nm as the pump source, corresponding to a conversion efficiency of 20.4%. By slightly adjusting the cavity length, the signal wavelength can be broadly tuned from 1001 to 1438 nm and the dual-wavelength tuning range is from 1001 to 1204 nm.