The Federal Bureau of Investigation, or FBI is the domestic intelligence and security service of the United States.
- Headquarters in Washington, D.C. 
- FBI Academy in Quantico 
- Las Vegas FBI field office 
- Philadelphia FBI field office 
- Pittsburgh FBI field office 
- Portland FBI field office 
- San Francisco field office 
- Director J. Edgar Hoover
- Deputy Director Gordon Cole - previously Regional Bureau Chief who oversaw the murder investigations of Teresa Banks, Laura Palmer, and Maddy Ferguson and the investigation of a mysterious dossier.
- Chief of Staff Denise Bryson - former DEA undercover agent.
- Bill Kennedy - Secretary of Denise Bryson.
- Special Agent Dale Cooper - assigned to the murder investigations of Laura Palmer and Maddy Ferguson in 1989. He was suspended due to accusations that he was acting outside his jurisdiction, and was allegedly involved in a cocaine trade. He was reinstated after proving his innocence.
- Diane Evans - Agent Cooper's secretary
- Agent Albert Rosenfield - forensics expert who assisted Cooper on the Laura Palmer and Maddy Ferguson investigations, in addition to determining the identity of an assailant who shot Cooper.
- Special Agent Windom Earle - worked as a liaison for the FBI in Project Blue Book.
- Special Agent Robin Masters - top agent of Cooper's promotion class.
- Special Agent Chester Desmond - assigned to investigate the 1988 murder of Teresa Banks, during which he disappeared without a trace.
- Special Agent Phillip Jeffries - disappeared in Buenos Aires in 1987, then re-emerged in Philadelphia in 1989 only to disappear again without a trace.
- Special Agent Tamara Preston - assigned by Cole in 2016 to determine the identity of an archivist who compiled a dossier concerning the town of Twin Peaks.
- Forensic specialist Sam Stanley - assisted Desmond in the Teresa Banks investigation. He subsequently was placed on administrative leave following a breakdown.
- Special Agent Roger Hardy - assigned to investigate the accusations against Cooper.
- Special Agent Frederic Nathan - FBI investigator working with Douglas Milford who interrogated Kenneth Arnold.
- Special Agent S.W. Reynolds - FBI liaison officer for Project Sign.
- Special Agent Randall Headley - Las Vegas-based agent.
- Agent Wilson - Las Vegas- based agent.
- Agent Gene - was at a school bus arrest alongside Chet Desmond and two other agents.
- Special Agent Aldo Smith
- Special Agent Bill Raum