Bilateral psoas abscess due to direct invasion of rectal cancer is a rare condition and has not been reported previously. A 57-year-old man with stage I rectal adenocarcinoma underwent low-anterior resection and adjuvant chemotherapy and showed complete response. However, 10 months after this operation, the disease recurred, with bladder invasion. Subsequently, he was admitted with low-grade fever accompanied by lower-back soreness and abdominal fullness for 1 month. Computed tomography (CT) of the abdomen showed several bilateral psoas muscle abscesses. Emergent CT-guided drainage of the bilateral abscess was performed, and a pus-like fluid was drained out. Microbiological culture of the pus revealed the presence of Salmonella group B, Bacteroides caccae, Bacteroides fragilis, and Peptostreptococcus indolicus. The patient recovered well after tube drainage and antibiotic therapy. Bilateral psoas muscle abscess due to direct invasion of rectal adenocarcinoma is unusual; however, with adequate drainage and administration of antibiotics, we were able to control this potentially fatal complication.