A brief, parent-led, transdiagnostic cognitive behavioral therapy (CBT) approach demonstrated utility among youth struggling with emotional problems during the COVID-19 pandemic. Homework completion between sessions is directly associated with psychotherapy treatment outcomes in non-parent-led CBT interventions. The present study sought to examine the relationship between homework completion and treatment response in a parent-led transdiagnostic CBT protocol. The first aim was to determine if completion of between session CBT homework was associated with change in symptom severity. The second aim was to determine if pre-treatment anxiety severity, social anxiety severity, and depressive symptoms were associated with treatment outcomes. One-hundred twenty-nine parents of youth (ages 5-13) with significant emotional problems received 6 sessions of telehealth parent-led CBT during the COVID-19 pandemic. Data on children's anxiety symptomology, clinical severity, homework compliance, depression, family relationships, perceptions on the impacts of the pandemic, treatment response, and therapists rating of symptom improvement were collected. Homework completion explained 9% of the variance in symptom improvement at post-treatment. Greater homework completion was associated with a significantly higher odds of treatment response (OR = 1.52, p = 0.001). Child anxiety severity, depressive symptoms, family relationships, and perceptions on the impacts of the COVID-19 pandemic were not significantly related to treatment outcome. Completion of homework predicted treatment outcomes in parent-led, transdiagnostic CBT for youth with emotional problems during the COVID-19 pandemic, while controlling for parent-rated anxiety, depression, family relationships, and COVID-related distress. Enhancing and targeting homework compliance between CBT sessions should be a central element of parent-led treatment.