Malignant gastrocolic fistula is a rare and challenging clinical entity characterized by nonspecific symptoms, often leading to delayed diagnosis and management. Imaging modalities such as barium studies, contrast-enhanced CT scans, and upper gastrointestinal endoscopy are crucial for diagnosis. We report the case of a 44-year-old man who presented with anorexia, significant weight loss, and nausea. Upper Gl endoscopy and colonoscopy revealed a gastrocolic fistula secondary to invasive adenocarcinoma involving the stomach extending into splenic flexure as a fistula. The patient underwent a D2 gastrectomy with Roux-en-Y gastrojejunostomy and left radical hemicolectomy. Histopathology confirmed moderately differentiated adenocarcinoma with lymph node involvement. This case highlights the importance of timely diagnosis and aggressive surgical management in improving outcomes in such rare malignancies.