The Briton beat Australia's Marc Polmans in the final round to continue his run of not dropping a set throughout the qualifying phase.
Broady, 26, had never previously won a match at Roland Garros but has been in brilliant form on the clay surface in Paris this week.
It is the first time the Stockport-born player has secured a place in the main draw of a Grand Slam, having reached the second round of Wimbledon in 2015 on a wildcard entry.
Andy Murray was among the few people courtside to support Broady - ranked 211th in the world - for his 7-6, 6-4 victory over 12th seed Polmans.
Broady will join Andy Murray, Johanna Konta, Dan Evans, Kyle Edmund, Cameron Norrie and Heather Watson in the draw on Thursday evening.
Roland Garros will become the first Grand Slam to welcome back fans following the coronavirus pandemic, but only 5,000 spectators will be allowed to attend each day following a recent spike in Covid-19 cases in France.
Additional reporting from the Press Association.