A power amplifier circuit includes a first transistor having a first terminal to which a voltage corresponding to a variable power supply voltage is to be supplied and a second terminal to which a radio-frequency signal is to be supplied, the first transistor being configured to amplify the radio-frequency signal, a bias circuit configured to supply a bias current or voltage to the second terminal of the first transistor, and an adjustment circuit configured to adjust the bias current or voltage in accordance with the variable power supply voltage supplied from a power supply terminal.