To find evidence of the content, construct, and criterion validity of the LABIRINTO scale for the diagnosis of autism spectrum disorder (ASD) in children aged 24-59 months. The scale was constructed in four stages: 1) items were defined based on an extensive literature review and discussions with autism and child development specialists; 2) child development specialists evaluated each item; 3) a preliminary version of the scale was applied to children diagnosed with ASD to enable any necessary adjustments; 4) the scale was then applied to 27 children with typical development and no neurodevelopmental disorder and 48 children with ASD. According to the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) and the Childhood Autism Rating Scale (CARS), clinical diagnosis constitutes the gold standard. The scale's psychometric indexes were appropriate for construct validity, with Kaiser-Meyer-Olkin = 0.94 and root mean square error of approximation = 0.000. Only one factor on the scale had a Cronbach alpha of 0.97. The receiver operating characteristic curve indicated a cutoff of 12, with a sensitivity of 100% and specificity of 100% for distinguishing children with ASD from those with typical development. This study confirmed the validity of the LABIRINTO scale.