In 1195, Richard I ("the Lionheart") of England commissioned certain knights to preserve the peace in unruly areas. They were responsible to the king for ensuring that the law was upheld, and preserved the "king's peace", and were known as "keepers of the peace".

An act of 1327 had referred to "good and lawful men" to be appointed in every county in the land to "guard the peace"; such individuals were first referred to as conservators of the peace, or wardens of the peace. The title "justice of the peace" derives from 1361, in the reign of King Edward III Plantagenet. The "peace" to be guarded is the "king's peace" or (currently) queen's peace, the maintenance of which is the duty of the Crown under the royal prerogative. Justices of the peace still use the power conferred or re-conferred on them in 1361 to bind over unruly persons "to be of good behaviour." The bind over is not a punishment, but a preventive measure, intended to ensure that people thought likely to offend will not do so. The justices' alternative title of "magistrate" dates from the sixteenth century, although the word had been in use centuries earlier to describe some legal officials of Roman times.

The Municipal Corporations Act 1835 stripped the power to appoint normal JPs from those municipal corporations that had it. This was replaced by the present system, where the Lord Chancellor nominates candidates with local advice, for appointment by the Crown.

Until the introduction of elected county councils in the 19th century, JPs, in Quarter Sessions, also administered the county at a local level. They fixed wages, regulated food supplies, built and controlled roads and bridges, and undertook to provide and supervise locally those services mandated by the Crown and Parliament for the welfare of the county.

Being an unpaid office, undertaken more for the sake of renown and to confirm the justice's standing within the community, the justice was typically a member of the gentry. The Justices of the Peace conducted arraignments in all criminal cases, and tried misdemeanours and infractions of local ordinances and bylaws. Towns and boroughs with enough burdensome judicial business that could not find volunteers for the unpaid role of Justice of the Peace had to petition the Crown for authority to hire a paid stipendiary magistrate.

In the centuries from the Tudor period until the onset of the Industrial Revolution, the JPs constituted a major element of the English (later British) government system, which had been termed sometimes squirearchy (i.e., dominance of the land-owning gentry). For example, historian Tim Blanning notes that while in Britain the royal prerogative was decisively curbed by the Bill of Rights 1689, in practice the central government in London had a greater ability to get its policies implemented in the rural outlying regions than could contemporary absolute monarchies such as France - a paradox due especially to JPs belonging to the same social class as the Members of Parliament and thus having a direct interest in getting laws actually enforced and implemented on the ground.

Women in Britain were not allowed to become JPs until 1919, the first woman being Ada Summers, the Mayor of Stalybridge, who was a JP by virtue of her office. Now in Britain 50% of JPs are women. Emily Murphy of Edmonton, Canada, preceded her by some three and a half years.

In special circumstances, a Justice of the Peace can be the highest governmental representative, so in fact 'gubernatorial', in a colonial entity. This was the case in the Tati Concessions Land, a gold-mining concession (territory) in the Matabele kingdom, until its annexation by the British Bechuanaland protectorate.

A justice of the peace in Australia is typically someone of good stature in the community who is authorised to witness and sign statutory declarations and affidavits and to certify copies of original documents. Criteria for appointment vary widely, depending on the state. For example, in Queensland, a justice of the peace (qualified) must complete an exam prior to being eligible for appointment, whereas in Victoria, a person need only prove good character by way of references.

Generally speaking, a justice of the peace cannot act in relation to a document which is to be used in a foreign country. One exception to this, however, is that countries in the Commonwealth frequently accept documents so certified, but this is largely dependent on local legislation.