Costa Rica at the 1988 Summer Olympics

• Silvia Poll — Swimming, Women's 200 metre Freestyle

Men's Marathon

• Ronald Lanzoni — 2:23.45 (→ 40th place)
• Juan Amores — 2:24.49 (→ 45th place)
• Luis López — 2:32.43 (→ 68th place)

• Humberto Aranda

• Henry Núñez Nájera

Men's 100m Backstroke

• Horst Niehaus
  1. Heat – 1:01.91 (→ did not advance, 42nd place)
• Eric Greenwood
  1. Heat – 1:03.11 (→ did not advance, 45th place)

Men's 200m Backstroke

• Horst Niehaus
  1. Heat – 2:12.83 (→ did not advance, 34th place)
• Eric Greenwood
  1. Heat – 2:15.42 (→ did not advance, 35th place)

Men's 200m Individual Medley

• Eric Greenwood
  1. Heat – 2:15.64 (→ did not advance, 43rd place)
• Horst Niehaus
  1. Heat – 2:16.16 (→ did not advance, 44th place)

Women's 50m Freestyle

• Carolina Mauri
  1. Heat – 27.96 (→ did not advance, 33rd place)

Women's 100m Freestyle

• Silvia Poll
  1. Heat – 56.16
  2. Final – 55.90 (→ 5th place)
• Carolina Mauri
  1. Heat – 1:00.14 (→ did not advance, 41st place)

Women's 200m Freestyle

• Silvia Poll
  1. Heat – 1:59.22
  2. Final – 1:58.67 (→ Silver Medal)
• Natasha Aguilar
  1. Heat – 2:10.22 (→ did not advance, 34th place)

Women's 100m Backstroke

• Silvia Poll
  1. Heat – 1:03.21
  2. Final – 1:03.34 (→ 6th place)

Women's 100m Breaststroke

• Sigrid Niehaus
  1. Heat – 1:16.65 (→ did not advance, 35th place)
• Montserrat Hidalgo
  1. Heat – 1:18.42 (→ did not advance, 36th place)

Women's 200m Breaststroke

• Montserrat Hidalgo
  1. Heat – 2:44.72 (→ did not advance, 37th place)
• Sigrid Niehaus
  1. Heat – 2:45.35 (→ did not advance, 38th place)

Women's 100m Butterfly

• Marcela Cuesta
  1. Heat – 1:07.66 (→ did not advance, 33rd place)

Women's 4 × 100 m Freestyle Relay

• Natasha Aguilar, Marcela Cuesta, Carolina Mauri, and Silvia Poll
  1. Heat – 3:59.67 (→ did not advance, 12th place)

Women's 4 × 100 m Medley Relay

• Silvia Poll, Sigrid Niehaus, Marcela Cuesta, and Carolina Mauri
  1. Heat – 4:31.75 (→ did not advance, 15th place)

• Rafael Elizondo