Pulsed, single-frequency laser sources have a potential use in laser spectroscopy or LIDAR application. We present a compact and reliable MOPA laser system with a small laser line width. The system is based on a passively q-switched, monolithic single-frequency master oscillator (NPRO) and a four stage Nd:YVO4 power amplifier. The amplifier was developed for the use in gravitational wave detectors and has already demonstrated excellent beam qualities and efficient amplification in the continuous wave regime. Transferring these properties to the pulsed regime is the scope of this paper.