But the report also touched on text messages between two FBI officials who later worked on Special Counsel Robert Mueller's investigation into alleged Russian meddling in the US election.
Peter Strzok, who was Mr Mueller's lead agent in the Russian inquiry, was having an affair with Lisa Page, an FBI lawyer who also temporarily worked on the Mueller investigation.
When Ms Page asked if Mr Trump would become president, Mr Strzok responded: "No. No he won't. We'll stop it."
The report called this "not only indicative of a biased state of mind but, even more seriously, implies a willingness to take official action to impact the presidential candidate's electoral prospects".
Christopher Wray said employees would be held accountable for any misconduct as a result of the report.