| Champ: | Željko Franulović |
| Runner: | Ilie Năstase |
| Score: | 6–3, 7–6, 6–1 |
| Before Name: | ATP Buenos Aires – Singles |
| After Name: | ATP Buenos Aires – Singles |
See main article: 1971 ATP Buenos Aires.
Željko Franulović defeated Ilie Năstase 6–3, 7–6, 6–1 to win the 1971 South American Open singles competition. Franulović was the defending champion.