Participating NOCs
Three nations made their first Summer Olympic appearance in Montreal: Andorra (which had had its overall Olympic debut a few months before in Innsbruck Winter Olympics), Antigua and Barbuda, Cayman Islands, and Papua New Guinea.
Numbers in parentheses indicate the number of athletes from each nation that competed at the Games.
| Participating NOCs |
- Andorra (3)
- Antigua (9)
- Argentina (70)
- Australia (182)
- Austria (60)
- Bahamas (10)
- Barbados (10)
- Belgium (106)
- Belize (4)
- Bermuda (22)
- Bolivia (4)
- Brazil (81)
- Bulgaria (160)
- Cameroon (4)WD
- Canada (391)
- Cayman Islands (4)
- Chile (7)
- Colombia (34)
- Costa Rica (5)
- Côte d'Ivoire (8)
- Cuba (150)
- Czechoslovakia (150)
- Denmark (69)
- Dominican Republic (11)
- Ecuador (5)
- Egypt (29)WD
- Fiji (2)
- Finland (89)
- France (213)
- East Germany (274)
- West Germany (289)
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- Great Britain (249)
- Greece (37)
- Guatemala (29)
- Haiti (12)
- Honduras (3)
- Hong Kong (25)
- Hungary (183)
- Iceland (14)
- India (26)
- Indonesia (7)
- Iran (84)
- Ireland (46)
- Israel (26)
- Italy (221)
- Jamaica (20)
- Japan (215)
- North Korea (41)
- South Korea (50)
- Kuwait (14)
- Lebanon (4)
- Liechtenstein (6)
- Luxembourg (8)
- Malaysia (23)
- Mexico (99)
- Monaco (10)
- Mongolia (33)
- Morocco (9)WD
- Nepal (1)
- Netherlands (103)
- Netherlands Antilles (4)
- New Zealand (84)
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- Nicaragua (14)
- Norway (68)
- Pakistan (24)
- Panama (8)
- Papua New Guinea (5)
- Paraguay (6)
- Peru (13)
- Philippines (14)
- Poland (224)
- Portugal (19)
- Puerto Rico (81)
- Romania (157)
- San Marino (10)
- Saudi Arabia (19)
- Senegal (23)
- Singapore (4)
- Soviet Union (412)
- Spain (115)
- Suriname (3)
- Sweden (122)
- Switzerland (54)
- Thailand (43)
- Trinidad and Tobago (12)
- Tunisia (17)WD
- Turkey (27)
- United States (403)
- Uruguay (9)
- Venezuela (31)
- Virgin Islands (18)
- Yugoslavia (90)
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^ WD: Athletes from Cameroon, Egypt, Morocco, and Tunisia competed on July 18–20 before these nations withdrew from the Games.
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- Guyana, Mali and Swaziland also took part in the Opening Ceremony, but later join to the Congolese-led boycott and withdrew from competition.