BACKGROUND: Deep vein thrombosis (DVT) can occasionally be secondary to mechanical compressions, such as in May-Thurner syndrome. To our knowledge, no cases of DVT associated with mechanical compression by fecal impaction in a pediatric patient have been previously reported. CASE PRESENTATION: An 18-year-old developmentally delayed female presented to the emergency department with swelling involving her left lower extremity. Cross-sectional imaging revealed a significant stool burden in the rectosigmoid colon compressing the left external iliac vein and causing secondary thrombosis. Thrombectomy successfully alleviated the clot burden. CONCLUSION: This case underscores the potentially serious implications of severe fecal impaction in the pediatric and adolescent populations.