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 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 first eight teams of the NLA then competed in the championship group and played a further double round-robin.
They took half of the points (rounded up to complete units) gained in the Qualification as bonus with them.