Cognitive tempo refers to the speed and accuracy of information processing during problem-solving and has been a central concept in developmental psychology and cognitive science. This chapter explores the intersection between cognitive tempo dysregulation and autism spectrum disorder (ASD), with a focus on cognitive disengagement syndrome (CDS)—a construct encompassing symptoms such as daydreaming, mental fog, lethargy, and slow processing speed. Originally conceptualized in relation to attention-deficit/hyperactivity disorder (ADHD), CDS has recently been examined in ASD populations, highlighting both overlapping and distinct features. The chapter reviews the historical development of CDS, its differentiation from ADHD, and its clinical relevance in ASD. Diagnostic challenges, comorbidities, and functional impairments across academic, social, and daily living domains are discussed. Evidence-based management strategies, including cognitive–behavioral therapy (CBT), environmental modifications, social skills training, and pharmacological interventions, are outlined. A case study illustrates the complexities of co-occurring ASD and CDS, emphasizing the need for tailored interventions. Collectively, the chapter provides an updated synthesis of the literature and practical insights into improving diagnostic accuracy and treatment planning for individuals with ASD presenting with CDS features.