The importance of the flat serve in tennis is well documented, with an abundance of research evaluating the service technique of adult male players. Comparatively, the female and junior serves have received far less attention. Therefore, the aims of this study were to quantify the flat serve kinematics in elite prepubescent, pubescent, and postpubescent female tennis players. Full body, racket, and ball kinematics were derived using a 22-camera Vicon motion capture system. Racket velocity was significantly lower in the prepubescent group than in the two older groups. In generating racket velocity, the role of the serving arm appears to become more pronounced after the onset of puberty, whereas leg drive and "shoulder-over-shoulder" rotation mature even later in development. These factors are proposed to relate to strength deficits and junior players' intentions to reduce the complexity of the skill. Temporally, coupling perception (cues from the ball) and action (body movements) are less refined in the prepubescent serve, presumably reducing the "rhythm" (and dynamism) of the service action. Practically, there appears scope for equipment scaling to preserve kinematic relevance between the junior and senior serve and promote skill acquisition.