PURPOSE: Despite growing evidence regarding nonsynostotic plagiocephaly and their repercussions on motor development, there is little evidence to support the use of manual therapy as an adjuvant option. The aim of this study was to evaluate the effects of a therapeutic approach based on manual therapy as an adjuvant option on treatment duration and motor development in infants with severe nonsynostotic plagiocephaly. METHODS: This is a randomised controlled pilot study. The study was conducted at a university hospital. Forty-six infants with severe nonsynostotic plagiocephaly (types 4-5 of the Argenta scale) referred to the Early Care and Monitoring Unit were randomly allocated to a control group receiving standard treatment (repositioning and an orthotic helmet) or to an experimental group treated with manual therapy added to standard treatment. Infants were discharged when the correction of the asymmetry was optimal taken into account the previous clinical characteristics. The outcome measures were treatment duration and motor development assessed with the Alberta Infant Motor Scale (AIMS) at baseline and at discharge. RESULTS: Asymmetry after the treatment was minimal (type 0 or 1 according to the Argenta scale) in both groups. A comparative analysis showed that treatment duration was significantly shorter (p < 0.001) in the experimental group (109.84 +/- 14.45 days) compared to the control group (148.65 +/- 11.53 days). The motor behaviour was normal (scores above the 16th percentile of the AIMS) in all the infants after the treatment. CONCLUSIONS: Manual therapy added to standard treatment reduces the treatment duration in infants with severe nonsynostotic plagiocephaly.