The systematic use of feedback from patients on treatment progress and treatment satisfaction is a promising method to increase treatment effectiveness. The extent to which this also applies to the treatment of children with severe psychiatric problems is not clear. We conducted a Randomized Controlled Trial (RCT) to study the effect of adding Feedback Informed Treatment (FIT) to care as usual in a child psychiatric sample. Quality of Life (QoL) was used as the primary outcome measure and symptom severity as the second. Fifty-one therapists from eight Autism Care Teams in a multi-center facility for Child and Adolescent Psychiatry (Karakter) participated and were cluster randomized to the FIT condition ( n = 4 teams) or the Care as Usual (CAU) condition ( n = 4 teams). Children aged 6–18 years, mainly with an Autism Spectrum Disorder (ASD) and treated in one of the Autism Care Teams were allocated to the FIT condition ( n = 86) or the CAU condition ( n = 80). Results indicated that adding FIT leads to an increased QoL [ F (2,165) = 3.16, p = 0.045]. No additional effects were observed for symptom severity decrease [ F (2,158) = 0.19, p = 0.825]. No interaction with time was found for QoL nor symptom severity. Adding FIT in a child psychiatric setting may increase QoL, but does not appear to decrease symptom severity as compared with CAU. It is suggested that FIT positively changes parents’ expectations. Results should be replicated in other child psychiatric samples and with an extended theoretical model.