The two teams drew 1-1 at a packed Centenario stadium in Montevideo Wednesday in the return leg of a play-off between the fifth-placed team in the South American qualifiers and the fourth-placed of the North and Central American and Caribbean region.
In the 69th minute, a header from veteran striker Sebastian Abreu, 33, appeared to give Uruguay a decisive lead before 65,000 spectators.
However, the home side's joy was shortlived. Only four minutes later another veteran, Walter Centeno, 35, made the most of a rebound in the box to put Costa Rica back in the race.
In the end, however, Uruguay made the most of their 1-0 weekend win in San Jose and advanced to the 2010 World Cup.
"This is priceless," a happy Abreu said after the game. "You always think that you could score the dream goal, the goal that can give you a World Cup qualification."
Coach Oscar Tabarez was equally thrilled.
"We are very, very satisfied about the fact that we could make it," he said. "When they drew, things got tough. They were one goal away from qualifying."
Uruguay star Diego Forlan described qualification as a dream come true, but admitted that the South American side "suffered" on the pitch.
The match was played in intense fog, and play was suspended for seven minutes in the second half amid clashes between Costa Rican substitutes and representatives of a television network that was broadcasting the game.
Uruguay have won two editions of the prestigious global event, but they date back to 1930 and 1950. Recent times have been a lot more disappointing: of the past four editions of the prestigious tournament, they only played one, in 2002, and even then they crashed out in the first round of play.
Now, they have the chance to write a fresh page in the country's World Cup history.