The PGA Championship was established for the purpose of providing a high-profile tournament specifically for professional golfers at a time when they were generally not held in high esteem in a sport that was largely run by wealthy amateurs. This origin is still reflected in the entry system for the Championship. It is the only major which does not explicitly invite leading amateurs to compete (it is possible for amateurs to get into the field, although the only viable way is by winning one of the other major championships), and the only one which reserves a large number of places, 20 of 156, for club professionals. These slots are determined by the top finishers in the club pro championship, which is held in June.

Since 1968, the PGA Tour has been independent of the PGA of America. The PGA Tour is an elite organization of tournament professionals, but the PGA Championship is still run by the PGA of America, which is mainly a body for club and teaching professionals. The PGA Championship is the only major that does not explicitly grant entry to the top 50 players in the Official World Golf Ranking, although it invariably invites all of the top 100 (not just top 50) players who are not already qualified.

List of qualification criteria as of 2010:

• All former PGA Champions.
• Winners of the last five U.S. Opens.
• Winners of the last five Masters.
• Winners of the last five Open Championships.
• The last Senior PGA Champion.
• The low 15 scorers and ties in the previous PGA Championship.
• The 20 low scorers in the last PGA Professional National Championship.
• The 70 leaders in official money standings on the PGA Tour (starting one week prior to the previous year's PGA Championship and ending two weeks prior to the current year's PGA Championship).
• Members of the most recent United States and European Ryder Cup Teams, provided they are in the top 100 of the Official World Golf Ranking as of one week before the start of the tournament.
• Winners of tournaments co-sponsored or approved by the PGA Tour since the previous PGA Championship (does not include pro-am and team competitions, but does include alternate events).
• The PGA of America reserves the right to invite additional players not included in the categories listed above.
• The total field is a maximum of 156 players. Vacancies are filled by the first available player from the list of alternates (those below 70th place in official money standings).