Introduction: The Sensory Motor Performance Scale (ECDSM2-15), recently developed using Delphi methodology, is a scale to assess the sensory and motor development of infants aged 2 to 15 months previously diagnosed with motor delay or cerebral palsy. This scale classifies the strategies used by infants into typical/normal, delayed, and atypical/patology and identifies the influence of the components of alignment, movement, and support base on functional outcome. Given its importance, there is a need to analyse the biometric characteristics of this scale. Objective: To determine the reliability and construct validity of the ECDSM2-15 scale. Patients and methods: A descriptive and prospective study was conducted in 454 boys and girls aged 2 to 15 months who showed delayed motor development or were diagnosed with cerebral palsy at the Teletón-Chile Institutes, Pedro Aguirre Cerda National Rehabilitation Hospital, and Amancay Neurological Rehabilitation Center. Reliability and construct validity analyses were performed. Results: Internal consistency and intra-observer variability showed a Cronbach's alpha > 0.80. Variability of evaluators versus control group showed a Kappa index> 0.60. Factor analysis showed a significant Kaiser-Meyer-Olkin index > 0.7 with Bartlett's sphericity test (p <.0001). The analysis of principal components with varimax rotation in the six subscales explained between 60 and 87% of the variance. Conclusion: The scale is reliable, consistent and valid in its construct and can be used in assessment, clinical follow-up and research.