Background: Colorectal cancer (CRC) during pregnancy is rare and presents diagnostic and therapeutic challenges. Aim: This case report focuses on a patient who presented with colorectal cancer during pregnancy. Case description: A 45-year-old female primigravid, pregnant woman, in the 20th week of gestation presented with complaints of multiple episodes of bloody diarrhea and tenesmus for the past 3 weeks. This was accompanied by poor appetite and weight loss (15 kg) since the onset of pregnancy. The patient also complained of lower back and abdominal pain. Investigations confirmed an obstructing rectosigmoid mass (15 cm) that could not be passed. The patient's pregnancy was terminated, and chemotherapeutic treatment was initiated. Clinical significance: With the clinical manifestations of CRC during pregnancy being non-specific, tumors are usually discovered at an advanced stage. This poses a challenge for physicians to treat such cases. This case contributes to the growing literature on pregnancies complicated by CRC and highlights the importance of high clinical suspicion and the need for a multidisciplinary team in tailoring treatment regimens in accordance with patient-centered care. Conclusion: This case report highlights the rarity of colorectal cancer during pregnancy and the challenges faced in the diagnoses and treatment.