We investigate the Fano line shape in electron transport through a quantum dot in presence of dephasing. The dephasing effect is introduced by the Büttiker model. We derive a generalized Fano formula for the conductance that includes the components of the standard Fano line shape and the Breit–Wigner line shape. According to this formula the Fano parameter |q| decreases when the dephasing strength increases by increasing the temperature. The increase of the half width of the resonance peak by increasing the temperature measured by Zacharia et al. [Phys. Rev.B64, 155311 (2001)] which is more rapid than expected from the ordinary theories is possibly attributed to the dephasing.