We investigated the effects of leg stiffness on running speed, jump height and leg power in 13 male 2^nd- and 3^rd-series ranked tennis players (23±3 years old, 73.2±8.4 kg, 1.81±0.06 m). Leg stiffness and jump height were assessed using jumping and hopping tests. Mean running speeds over 20 m and 40 m (speed₂₀ and speed₄₀, respectively) were determined from a sprint test. Theoretical maximal leg power (P_maxth) was extrapolated from a force-velocity test performed on a cycle ergometer. Leg stiffness averaged 478.7±181.7 N.m⁻¹.kg⁻¹ (34 808±12 573 N.m⁻¹). It was significantly correlated to speed₂₀ and counter movement jump height (r=0.60, P=0.028 and r=0.58, P=0.0407, respectively). There were also significant correlations between P_maxth and counter-movement jump height (r=0.59, P=0.0335) and between P_maxth and speed₄₀ (r=0.58, P=0.0393). This study characterizes leg stiffness in tennis players and brings new information concerning the way it is related to several other muscular biomechanical parameters.