Little is known about parents' motivations to engage in Internet mediation nor about how parents may influence each other's Internet mediation practices. The present study uses triadic data, with reports from the mother, the father, and the adolescent child from the same family (N = 357). Structural equation modeling (SEM) is applied for testing the relationship between parents' concerns over Internet risks, parents' engagement in mediation practices, and the adolescent's engagement in risk behavior on social network sites (SNSs). Parents' risk perception was not related to mediation practices, but the mother's risk perception had a positive effect on the father's engagement in parental mediation. Parental mediation predicted less online contact with strangers by the adolescent. The results show that both parents contribute individually to their adolescent child's safe Internet use, which stresses the importance of involving both parents in parental mediation research.