Introduction: The successful treatment of adolescents almost always requires parents’ involvement in the treatment process. Thus, parental involvement will impact further treatment, especially concerning the acute management of self-harming behavior of their children. Parental burden or low parental motivation for treatment can significantly affect the success of the intervention. Therefore, this study aimed at investigating how especially motivational factors of the adolescents and parents, as well as stressors of the parents, affect the course of non-suicidal self-injury (NSSI) after an acute psychiatric emergency presentation. Methods: Ninety-six adolescents aged 11–18 years who have been presented to an emergency service at a child and adolescent psychiatry clinic for suicidal and/or NSSI behavior were recruited together with their accompanying parents within the framework of a specified diagnostic procedure. This included detailed questionnaire and interview procedures for psychiatric assessment. The extent of parental stress and parents’ motivation for treatment and its relations to adolescents’ NSSI and own treatment motivation have been investigated in a follow-up examination in the aftermath of the acute presentation. We predicted adolescents’ NSSI at follow-up based on their own motivation and parental motivation and stress. Results: Data analysis demonstrated that higher adolescents’ treatment motivation was associated with higher parental stress. Also, higher parental treatment motivation was correlated with a higher degree of parental distress. Furthermore, parents showed lower treatment motivation when their children engaged in NSSI for a longer duration. Finally, lower adolescents’ motivation and lower parental stress due to own parental concerns were predictive for higher adolescents’ NSSI frequency at follow-up investigation. Discussion/Conclusion: Patients as well as their parents who present for an emergency service are especially likely to be exposed to increased stress and strain factors. During treatment, additional focus should be placed on parental stress and parental and adolescents’ treatment motivation. Identifying and addressing deficits in motivation, increases in parental stress, as well as offering support could favorably impact future NSSI behavior.