United States' officials had told the 31-year-old former world champion he had not achieved the qualifying mark of 16.85 metres as his indoor performances this year did not count.
But Harrison, whose victory at the US trials with 18.01 metres was invalid for qualifying purposes because of wind assistance, took his case to the international authority, which ruled in his favour.
Edwards will now have to face two of the three other triple jumpers who have surpassed 18 metres, as Harrison joins the reigning Olympic champion, Mike Conley.
Harrison, whose indoor mark of 17.05 metres at Reno in February eventually proved sufficient to allow him to compete here, was angry about the actions taken - or not taken - by the US Track and Field authorities.
After his opening jump at the trials, he passed on his other five attempts, believing that he had done enough to win and that his indoor marks would give him the qualifying distance.
"During the competition, with our coaches there, someone should have come down after they saw me passing three jumps and said: 'Hey, you don't have the qualifying mark. You might want to take an extra jump.' I don't think they even went through the effort of checking."
Harrison's motivation to do well stems as much from a desire to beat Conley as anything else. "Conley's name overshadows everything I have ever done," he said. "To get the attention, I have to do something extra special. The thing he has that I don't is an Olympic gold."
In the meantime, pressure has been growing upon Mike Turner - the doctor who told BBC's Panorama programme this week that 75 per cent of athletes in Atlanta had probably taken performance-enhancing drugs - to back up his claims.
Turner, who is a member of the British Olympic Association's medical committee as a representative of the Lawn Tennis Association, has been asked by the British Athletic Federation either to substantiate his comments by Friday, or consider his position on the BOA committee.
Malcolm Brown, Britain's team doctor, added his weight to the argument by hinting that he would resign from the BOA committee if Turner did not.
"The team are incensed by these comments," said the BAF spokesman Tony Ward. "He is being cheap. A lot of mud has been flung at us over the years, and we have been too tolerant.
"This is the most tested British team we have sent to a major championships in the history of athletics. We have conducted more than 300 tests in the last three to four months, and all of the 80-strong team are clean. That is fact, not innuendo."
Dean Capobianco, the Australian sprinter suspended after testing positive for the banned steroid stanozolol, has taken part in an independent hearing by telephone link-up and is awaiting the decision of the QC in charge of the case, Robert Ellicott.