A crystal oscillator circuit comprises a crystal; oscillator circuitry for generating a crystal oscillation signal at an oscillation frequency; and a kick-start circuit for injecting pulses into the crystal during a start-up period. The oscillator circuitry comprises a differential pair of transistors and can operate in an oscillating mode or a start-up mode. In the oscillating mode, the differential pair of transistors are cross-coupled so that a gate terminal of one transistor is coupled to a drain terminal of the other transistor, and vice versa, and the drain terminals are coupled to the crystal to generate the crystal oscillation signal. In the start-up mode, the kick-start circuit drives the gate terminals of the transistors with said pulses. This crystal oscillator circuit has a decreased start-up time compared to prior art solutions and a reduced influence of parasitic oscillations.