The Diamondbacks became the first major league team in Arizona, starting the 1998 season. On April 4, the franchise posted their first victory over the Giants in a 3-2 win. They lost 97 games their first year.

In the off-season, Randy Johnson agreed to a four-year contract, giving the D-Backs a legitimate ace.

In 1999 the Diamondbacks exploded to win 100 games and the NL West division crown. Johnson, Womack, and Luis Gonzales led the team. Gonzales batted safely in 30 straight games, setting a team record. In the playoffs they were defeated by the Mets 3 games to 1.

The 2000 season was disappointing, as Arizona slumped to 3rd place.

In 2001 the Diamondbacks won the World Series! All the pieces came together in 2001 and a great pitching staff and good players were able to win the biggest prize even for a young team. Phoenix - the only city with four major sports franchises to never win a title in any sport, finally won their long awaited crown in a dramatic seven-game World Series against the New York Yankees. The Diamondbacks, anchored by Cy Young-caliber seasons by Johnson and Curt Schilling and a 57-home-run season by Luis Gonzalez, won 92 games and their second division title. After dispatching the Cardinals in a tight five-game series, the D-Backs defeated the Braves in the NLCS to advance to and win their first World Series.

In 2002 the team rode Schilling and Johnson once again, both pitchers winning at least 22 games and striking out at least 300 batters. But late season injuries took the wind out of their sails, even as they won their second straight NL West title. The Cardinals rocked Johnson in Game One of the NL Division Series on their way to an improbable sweep.

In 2004, the Diamondbacks finished last in the National League Division with a 51-111 record losing more games than their 1st year when they lost 97 games. Upon the completion of the 2004 season in January 2005, Randy Johnson, their star pitcher, was traded to the New York Yankees. This move was made to free up money so they can begin to rebuild their team into a Championship club again.

In 2006 the Diamondbacks finished with a 76-86 record and in 4th place.