Costas has frontlined many Olympics broadcasts for NBC. They include the Olympics in Barcelona in 1992, Atlanta in 1996, Sydney in 2000, Salt Lake City in 2002, Athens in 2004, Torino in 2006, Beijing in 2008, and Vancouver in 2010. He discusses his work on the Olympic telecasts extensively in a book by Andrew Billings entitled Olympic Media: Inside the Biggest Show on Television. A personal influence on Costas has been legendary ABC Sports broadcaster Jim McKay, who hosted many Olympics for ABC from the 1960s to the 1980s.
During the 1992 Barcelona and 1996 Atlanta Opening Ceremonies, Costas' remarks on the China Team's possible drug use caused an uproar among the American Chinese and international communities. Thousands of dollars were raised to purchase ads in the Washington Post and Sunday New York Times, featuring an image of the head of a statue of Apollo and reading: "Costas Poisoned Olympic Spirit, Public Protests NBC." However, Costas' comments were made subsequent to the suspension of Chinese coach Zhou Ming after seven of his swimmers were caught using steroids in 1994. Further evidence of Chinese athletes' drug use came in 1997 when Australian authorities confiscated 13 vials of Somatropin, a human growth hormone, from the bag of Chinese swimmer Yuan Yuan upon her arrival for the 1997 World Swimming Championships. At the World Championships, four Chinese swimmers tested positive for the banned substance Triamterene, a diuretic used to dilute urine samples in order to mask the presence of anabolic steroids. Including these failed drug tests, 27 Chinese swimmers were caught using performance enhancing drugs from 1990 through 1997; more than the rest of the world combined.