The 2005 Major League Baseball season was notable for the league's new steroid policy in the wake of the BALCO scandal, which enforced harsher penalties than ever before for steroid use in Major League Baseball. Several players, including veteran Rafael Palmeiro, were suspended under the new policy. Besides the cracking down on steroids, it was also notable that every team in the NL East finished the season with at least 81 wins (at least half of the 162 games played). Additionally it was the first season featuring a baseball team in Washington, D.C. since the second iteration of the Washington Senators last played there in 1971; the Washington Nationals had moved from Montreal, the first relocation of a team in 33 years.
The Anaheim Angels changed their name to the Los Angeles Angels of Anaheim.
The season ended when the Chicago White Sox defeated the Houston Astros in a four-game sweep in the World Series, winning their first championship since 1917.
This was the last season in which no no-hit games were pitched until 2025; 2005 was also only the 6th year since 1949 in which no such games were thrown.
This was the first season since 1993 that all teams played at least 162 games with no cancellations.
<section begin=Bracket/> <section end=Bracket/> Note: Two teams in the same division could not meet in the division series.
ñhosted the MLB All Star Game
This was the fifth season that national television coverage was split between ESPN and Fox Sports. ESPN and ESPN2 aired selected weeknight and Sunday night games, and selected Division Series playoff games. Fox televised Saturday baseball, the All-Star Game, selected Division Series games, both League Championship Series, and the World Series.
<span style="font-size:90%">Major League Baseball seasons since 1901 without a no-hitter pitched are 1909, 1913, 1921, 1927–1928, 1932–1933, 1936, 1939, 1942–1943, 1949, 1959, 1982, 1985, 1989, 2000, 2005 and 2025.</span>