This study retrospectively evaluated long-term outcomes of 18 cats diagnosed with small intestinal adenocarcinoma, based on surgical versus non-surgical treatment and the presence or absence of metastasis at the time of surgery. Ten cats had surgery and histopathologic confirmation of adenocarcinoma and 8 cats did not have surgery but had cytologic diagnosis of adenocarcinoma. Median survival of cats with adenocarcinoma that underwent surgical excision was 365 days and 22 days for those with suspected adenocarcinoma that did not undergo surgery (P = 0.019). Median survival of cats was 843 days for those without evidence of metastatic disease at the time of surgery and 358 days for those that had (P = 0.25). In conclusion, surgical excision is beneficial in the treatment of small intestinal adenocarcinoma in the cat, including those patients with metastasis, and may result in a significantly longer survival time compared with patients which do not have their mass surgically excised.