Abstract Objective Cognitive disengagement syndrome (CDS), previously known as sluggish cognitive tempo (SCT), presents with symptoms like mind-wandering, hypoactivity, and mental fogginess. There is a relatively high prevalence (23.7%) of CDS in survivors of acute lymphoblastic leukemia (ALL), although the neuropathology remains poorly understood, potentially involving autonomic nervous system dysfunction. Cognitive late effects, including slowed speed, inattention and executive dysfunction can occur post-cancer treatment. This case highlights the need for regular assessment of CDS, particularly in the pediatric cancer population. Given the symptom overlap it is important to discuss onset, duration, and variability of symptom presentation to rule-in/out the role of cognitive late effects. Method “Alex,” a 14-year-old, B cell ALL survivor, was struggling academically nine years post-treatment. She and parents reported slowness, fatigue, trouble concentrating, and social withdrawal, despite medical stability. She received two years of psychotherapy for anxiety and depression without improvement. Results Alex had average intellectual and cognitive functioning, with mild executive dysfunction. Despite reported slowness in daily activities, processing speed was average. Parent and self-report forms indicated significant problems with executive functioning, somatic symptoms, and inattention. Parents indicated significant symptoms on the SCT scale. Alex’s cognitive profile suggested ADHD-I with features consistent with CDS. Conclusions Discrepancies between testing scores and daily life challenges were inconsistent with cognitive late effects. Her physical symptoms (e.g., fatigue, social withdrawal) did not improve with mood as expected with depression. Identifying these discrepancies and symptom timeline was crucial in diagnosing CDS and guiding interventions, leading to a sense of relief and direction for Alex and her family.