In 2018, Nassar was sentenced for molestation of gymnasts.
The FBI agents made numerous mistakes and covered up his abuse for months after the case was opened.
Rachael denhollander, who was the first woman to accuse Nassar publicly, stated that although the US justice department's internal audit revealed serious flaws, there was no accountability.
"This report exposes corruption, but its conclusion states 'doesn’t matter. In a series tweets, she explained that nothing is happening now. "These agents are now retired on government pensions, while survivors fight for their lives."
The FBI released a statement Wednesday acknowledging the findings of the report and calling the handling Nassar's file "inexcusable" and "a discredit to the organization".
The agency stated that it would take all steps necessary to prevent the same mistakes from happening again.
A 119-page report from the Department of Justice InspectorGeneral found that, despite serious allegations against Nassar's character, the FBI field office at Indianapolis was slow to respond.
The report stated that Nassar continued to commit sexual assaults during this period.
- The 156 women that confronted a predator
The report stated that two FBI agents lied to cover up their mistakes when confronted with their mistakes.
Jay Abbott, one of the FBI agents was in talks with USA Gymnastics officials to discuss a job at the Olympic Committee at the time that the allegations were made. In 2018, Mr Abbott resigned from the agency.
Unnamed employees will not be working on FBI matters until internal investigations are complete.
Josh Minkler, Mr Abbott's lawyer, stated in a statement to Reuters that his client "thanks law enforcement officers, prosecutors, and those who brought Larry Nassar before justice".
In 2018, the FBI launched an internal review of how it handled the Nassar case. The disgraced doctor was sentenced and will spend the rest of his life behind bars.
More than 330 girls and women from USA Gymnastics, Michigan State University, and Olympic athletes Simone Biles or Aly Raisman have accused him of sexual abuse.