Aim and background: Signet ring cell carcinoma (SRCC) is a rare variant of adenocarcinoma, typically presenting as gastric carcinoma and infrequently in the breast. Metastasis from breast cancer to the colorectum is notably rare. This case report documents a unique presentation of primary breast invasive lobular SRCC with colorectal metastasis and highlights the diagnostic challenges of such cases. Case description: A 52-year-old woman with a history of type II diabetes mellitus presented with obstipation, abdominal pain, and significant weight loss. Initial evaluations suggested colorectal malignancy. However, further diagnostic procedures, including colonoscopy, computed tomography scans, positron emission tomography computed tomography scan, breast imaging, and histopathological examinations revealed a more complex scenario. The identified rectal mass was a metastatic manifestation of primary breast cancer, specifically an invasive lobular carcinoma with a signet ring cell variant. The rarity of SRCC metastasizing from the breast to the colorectum adds complexity to the diagnostic process. Despite the typical negative expression for CK7 and CK20 in breast SRCC, this case exhibited a positive E-cadherin immunoreactivity. Hormone receptor analysis played a crucial role in distinguishing the primary site of the malignancy. Conclusion: This case contributes valuable insights into the rare occurrence of breast SRCC metastasizing to the colorectum. It highlights the importance of considering metastasis in differential diagnoses and advocates for multidisciplinary management in complex oncological cases. Clinical significance: Despite the aggressive nature and complex treatment requirements of such cases, the importance of a tailored approach in managing metastatic breast cancer is highlighted. The need for further research to better understand and manage this rare malignancy subtype is evident.