The study of developmental trajectories in metaphor comprehension has prevailingly addressed typically developing children (TD children, henceforth), and more recently, also children with Autism Spectrum Disorder (ASD, henceforth). Monitoring these trajectories longitudinally illuminates potentialities and residual weaknesses in children having had difficulties in handling figurative language. The present study describes the case of a child with ASD, M.M. (a pseudonym) who received a specific intervention when he was 8,10 to improve sensory metaphor comprehension. Afterwards, his capability to explain physico-psychological metaphors, which are more complex, was monitored across a 5-year span. During this interval, M.M was assessed three times at approximately 18 months distance, and compared to a group of TD children matched by age, school grade, number and dates of assessment. The results at a test measuring physico-psychological metaphors are analysed. Beyond quantitative differences in performance, differences in the developmental trajectories of M.M. and the TD children are outlined. Some implications for clinical assessment and intervention with children with ASD are also pointed out.