A probation officer works for the criminal justice system, supervising offenders who have not yet been sentenced for crimes or individuals who have been sentenced to probation or given suspended sentences. This differentiates a probation officer from a parole officer, who supervises prisoners who have been released early for good behavior. In some regions, the functions of parole and probation officer are combined for greater efficiency.

Primarily, a probation officer ensures that the terms of a probation are enforced. For example, a court may agree to put someone on probation if they agree not to consume drugs or alcohol, and to refrain from socializing with certain people. The probation officer meets with this individual along with family, friends, and employers, on a regular basis, and he or she may perform random visits or tests to ensure that the person is complying with the probation restrictions.

The number of people supervised by a probation officer varies, depending on region and the number of people out on probation at any given time. Most criminal justice systems try to keep people with the same officer, encouraging continuity of care. This also ensures that changes in behavior are quickly noted, as when someone meets with a probation officer once a month for three years, a sudden change in personality will be fairly obvious.

These members of the criminal justice community may or may not be law enforcement officers, depending on their training and the region. If a probation officer is a member of law enforcement, he or she can carry a weapon and serve arrest warrants. If not, the court may still grant a probation officer a concealed weapon permit for the purpose of self-protection in this potentially dangerous job.

In addition to supervising people, probation officers also write regular reports on their charges. These reports make note of good behavior, lapses on the terms of the probation, and missed or rescheduled meetings. While on probation, someone is subject to random searches or the revocation of probation based on information filed in this reports. These reports are also considered during the sentencing process.

Typically, a probation officer works with either adults or juveniles, but not both. He or she often has a degree in social work or a related field, in addition to specific training as a probation officer. In addition to monitoring offenders, probation officers also help to work on treatment and rehabilitation plans, and they may offer counseling and similar services as well.