The findings, released Thursday by the Department of Homeland Security's acting inspector general, came 18 months after more than a dozen Secret Service agents and officers were implicated in a prostitution scandal on President Obama's trip to Cartagena, Colombia, the Washington Post reported.
The Post obtained a copy of the report late Thursday.
Congress sought the report after Secret Service officials testified that the behavior in Columbia was an anomaly and not indicative of a broader institutional problem.
The report determined there have been isolated instances of misbehavior, the Post said.
Investigators recommended the Secret Service implement 14 new guidelines that would identify and address employee misconduct, noting that the agency has implemented 11 of the recommendations so far.
"Although individual employees have engaged in misconduct or inappropriate behavior, we did not find evidence that misconduct is widespread in USSS [U.S. Secret Service]," the Office of the Inspector General's report concluded. "Furthermore, we did not find any evidence that USSS leadership has fostered an environment that tolerates inappropriate behavior."
The report said the Secret Service "should continue to monitor and address excessive alcohol consumption and personal conduct within its workforce."
The evaluation relied mainly on an anonymous online survey of Secret Service agents. Investigators indicated 2,575 of the agency's 6,500 employees completed the questionnaire. Of those who completed the survey, 83 percent said they weren't personally aware of sexual misconduct such as the incident in Cartagena.
The office's acting inspector general, Charles K. Edwards, stepped down Monday. He and his deputies were under Senate investigation for altering reports to scrub information that may embarrass the Secret Service and the Obama administration.
The Post said the report was signed by Carlton I. Mann, who replaced Edwards as acting inspector general.