In this randomized controlled trial (RCT), the digital socio-emotional competence training Zirkus Empathico was tested in 74 Central European children (5.1 (0.9) years; 34 females) within a longitudinal design (three time points: T1 = pre-training; T2 = immediately following 6-week training, T3 = 3-month follow-up). The pre-registered primary outcome was empathy, secondary outcomes included emotion recognition, prosocial behavior, and behavioral problem reduction; furthermore, children's neural sensitivity to facial expressions quantified with event-related potentials. Compared to controls (N = 38), Zirkus Empathico participants (N = 36) showed increases in empathy (d = 0.28 [-0.17, 0.76]), emotion recognition (d = 0.57 [0.01, 1.06]), prosocial behavior (d = 0.51 [0.05, 0.99]) and reduced behavioral problems (d = 0.54 [0.08, 1.03]). They also showed larger P3 amplitudes to happy vs. angry and neutral facial expressions post-training. Thus, Zirkus Empathico may be a promising digital training for social competence in preschoolers.