Background: Abnormal sensory reactivity is considered one of the diagnostic criteria for autism spectrum disorders (ASD) and has been associated with autism severity, poorer functional outcomes, and behavioral difficulties across the lifespan. Its early characterization could provide valuable insights into the processes favoring the instantiation of maladaptive behaviors. Objectives: The present study has two aims: (1) to describe the sensory profile of preschool children with ASD compared with an age-matched population of children with a diagnosis of language disorder (DLD) and typically developing (TD) control peers; (2) to explore within each group whether the sensory alterations play a predictive role in the instantiation of emotional and behavioral issues. Methods: The parents of 42 ASD, 18 DLD, and 56 TD filled out the Sensory Processing Measure—Preschool (SPM-P). To gather information on competencies, behaviors, and emotional problems of children, the Child Behavior Checklist 1½-5 (CBCL 1½-5) was also administered. Results: On the SPM-P, ASD and DLD samples generally had scores more compromised than control peers. The contrast between ASD and DLD was reflected in a higher (and highly significant) impairment on the social participation and hearing subscales, suggesting a greater sensitivity and a possible specificity of these scores for ASD. More importantly, linear regression analyses revealed a strong and predictive association for ASD children with SPM total scores explaining more than 50% of the variance of the CBCL 1½-5 total scores (p < 0.001). Conclusions: Our findings reinforce the need to detect the abnormal sensory profiles of ASD already at an early stage and during clinical evaluations. Due to the impact on the emotional and behavioral manifestations, such a procedure has significant clinical and social implications, potentially guiding the development of new interventions relying on multisensory strategies.