Parametric studies of passive Q-switching and mode-locking in a Nd3+ : YVO4-Cr4+ : YAG laser were theoretically carried out. Simultaneous mode-locking and Q-switching was also experimentally studied. It was found that over 90% of the output power could be mode-locked in a diode-pumped passively Q-switched Nd3+ : YVO4-Cr4+ : YAG laser. The average pulse duration of the mode-locked pulse train was estimated to be around 110 ∼ 150 ps. The highest peak power of a single pulse near the maximum of the Q-switched envelope was greater than 100 kW.