Objective. Although triple-negative breast cancer (TNBC) has been considered to be an aggressive disease, the outcome of small-tumor (T1abcN0M0) TNBC and the effect of adjuvant chemotherapy on TNBC survival remain controversial. Methods. We identified 4565 T1abcN0M0 TNBC patients in the Surveillance, Epidemiology, and End Results (SEER) database from January 1, 2010, to December 31, 2015. After propensity score matching (PSM), 3214 patients were finally analyzed. Survival rates were compared among T1a, T1b, and T1c patients and between patients with and without adjuvant chemotherapy. Results. We classified 424, 1040, and 3101 cases as T1a, T1b, and T1c TNBC, respectively. A total of 2760 (60.5%) patients received adjuvant chemotherapy, accounting for 25.5%, 56.0%, and 66.8% of T1a, T1b, and T1c patients, respectively. Rates of 5-year breast cancer-specific survival (BCSS) for T1a, T1b, and T1c patients receiving chemotherapy were 97.8%, 94.1%, and 94.5%, respectively, compared with 97.2%, 94.0%, and 89.9% in patients without chemotherapy. Patients receiving adjuvant chemotherapy had higher 5-year BCSS (94.5% vs. 89.9%, P = 0.004) in the T1c subgroup, but no significant difference was detected in T1a or T1b patients due to adjuvant chemotherapy. Conclusion. Small-tumor TNBC showed very good prognosis. Adjuvant chemotherapy improved prognosis in T1c TNBC cases to a greater extent than in T1a and T1b patients. More large-scale clinical trials are needed, and further study should be conducted to determine appropriate adjuvant chemotherapy for T1c TNBC patients.