This study aimed to determine the incidence of adhesive small bowel obstruction (SBO) after primary colorectal cancer surgery and the outcomes of conservative management using gastrointestinal tubes in such cases. Between October 2000 and December 2005, 2,586 primary colorectal cancer patients underwent consecutive operations and were followed up completely for a median of 38 months. During the follow-up periods, 119 patients with 130 consecutive cases of adhesive SBO underwent conservative management using nasogastric tubes and long intestinal tubes. The overall adhesive SBO rate was 5.0% in 38 months of follow-up, and the observed incidence rate was 0.0013 per patient-month. Of the 130 cases, 104 cases (80%) were successfully treated by conservative management, and the symptoms of SBO were resolved by the sixth day (range 1 to 22). Twenty-six cases (20%) underwent surgery because of lack of clinical improvement (17) or signs of strangulation (9). The high success rate indicates that initial conservative management with intestinal decompression using gastrointestinal tubes is recommended for patients with adhesive SBO after primary colorectal cancer surgery.