| Competition: | Nationalliga A |
| Season: | 2001–02 |
| Winners: | Basel 9th title |
| Relegated: | Sporting: Aarau Luzern License: None |
| League Topscorer: | Christian Giménez (28) Richard Núñez (28) |
| Prevseason: | 2000–01 |
| Nextseason: | 2002–03 |
The 2002–03 season of the Swiss Nationalliga contained two divisions, each with twelve clubs. The top tier was called Nationalliga A (NLA) (French: Ligue Nationale A, Italian: Lega Nazionale A) and the second tier was named Nationalliga B (NLB).
The season was divided into two phases. The first of which was the qualification phase, and within the divisions the teams played a double round-robin, one at home and the other away. The divisions were then split. The first eight teams of the NLA then competed in the championship group and played a further double round-robin. The teams in ninth to twelfth position competed with the top four teams of the NLB in a promotion/relegation group to decide which four teams would play top tier next season. The other eight teams of the second tier competed in a play-out against relegation to the 1. Liga and the last two teams were to be relegated.
This was the second last season in which the Swiss championship would be competed in this format. It was already in planning that in two seasons the Nationalliga would be renamed to Swiss Football League and the championships were to be renamed and reformed.
The first eight teams of the qualification then competed in the Championship Round. They took half of the points (rounded up to complete units) gained in the Qualification as bonus with them.