The 1998Arizona Cardinals season was the franchise's 78th in the National Football League. It was the Cardinals' 11th season in Arizona. The club posted its first winning record since 1984, appeared in the postseason for the first time since 1982, its first postseason appearance in a non-strike season since 1975, and won its first postseason game since 1947. It was the Cardinals' first playoff appearance in its tenure in Arizona. (The team moved to Phoenix from St. Louis after the 1987 season.)
Statistics site Football Outsiders calls the 1998 Cardinals "one of the greatest fluke teams of all time ... who went 9–7 despite getting outscored by their opponents 378–325. They rank[ed] 25th [statistically] below three different 4–12 teams. [T]hey were a colossal fluke, despite the fact that they managed to win a playoff game in a huge upset over Dallas. ... The Cardinals went 6–3 over their final nine games, but all six wins came against teams that were 6–10 or worse, and all six wins came by either two or three points. The next year, they were back to 6–10...."Football Outsiders states that the 1998 Cardinals are the third-worst team (behind the 2004 Rams and 2010 Seahawks) to qualify for the NFL playoffs since they began calculating ratings.