| Season: | 1998–99 |
| Competition: | Nationalliga A |
| Winners: | Servette 17th title |
| Relegated: | Sion Young Boys |
| League Topscorer: | Alexandre Rey (19 goals) |
| Prevseason: | 1997–98 |
| Nextseason: | 1999–2000 |
Teams in the Swiss National League A played 22 games in the 1998–99 football season, with an eight-team playoff.
The Qualification Round to the League season 2001–02 was contested by twelve teams. The first eight teams of the First Stage (or Qualification) were then to compete in the Championship Playoff Round. The teams in ninth to twelfth position completed with the top four teams of the Nationalliga B in a Nationalliga A/B Playoff round.
At the end of the season Servette won the championship.
The first eight teams of the qualification phase competed in the Championship round. The teams took half of the points (rounded up to complete units) gained in the qualification as bonus with them.
The teams in the ninth to twelfth positions in Nationalliga A competed with the top four teams of Nationalliga B in a Nationalliga A/B promotion/relegation round.
The last eight teams of the qualification phase competed in the relegation group against relegation to the 1. Liga. The teams took half of the points (rounded up to complete units) gained in the qualification as bonus with them.