Monitors are the clones' overseers. Their task is to watch over their subjects closely, while not interfering with the subjects' natural choices. To achieve this, monitors integrate themselves into the clones' personal lives as deeply as possible, usually posing as either a close friend or loved one.
Not all monitors are aware of their true purpose or the origins of their subjects. Some are part of the program willingly, some are blackmailed into participating and some are simply led to believe the entire project is innocuous with hefty compensations. Any data collected by the monitors is sent back to their superiors, amongst which included Olivier Duval and Dr. Aldous Leekie.
- Ethan Duncan †, former monitor and father of Rachel Duncan
- Susan Duncan † (possibly; status unknown), former monitor and mother of Rachel Duncan
- Daniel Rosen †, former monitor and lover of Rachel Duncan
- Paul Dierden †, former monitor and boyfriend/lover of Elizabeth Childs, Sarah Manning (unknowingly) and Rachel Duncan
- Donnie Hendrix, monitor and husband of Alison Hendrix
- Delphine Cormier, monitor and ex-girlfriend of Cosima Niehaus
- Greg, monitor and boyfriend of Jennifer Fitzsimmons
- Sammy†, former monitor and friend of Tony Sawicki
- Marion Bowles † (possibly; status unknown), monitor and mother figure of Charlotte Bowles
- Emi †, former monitor and ex-girlfriend of Cosima Niehaus
- Hector †, former monitor and boyfriend of Krystal Goderich
- Matti †, former monitor and "uncle" of Veera Suominen
- Since Rachel Duncan grew up self-aware, she is the only clone that knew of her monitors from the start. She is also the only one to have had more than one monitor throughout the series.
- Paul Dierden is the only person known to have monitored multiple clones.
- Krystal Goderich has apparently had at least three monitors rotating on a bi-annual schedule, demonstrated by her observation that her past boyfriends always seem to leave her every 2 years without warning or reason.