By the arrangements of the Canadian federation, Canada's monarchy operates in New Brunswick as the core of the province's Westminster-style parliamentary democracy. As such, the Crown within New Brunswick's jurisdiction is referred to as the Crown in Right of New Brunswick (French: couronne du chef du Nouveau-Brunswick), His Majesty in Right of New Brunswick (French: Sa Majesté du chef du Nouveau-Brunswick), or the King in Right of New Brunswick (French: le roi du chef du Nouveau-Brunswick). The Constitution Act, 1867, however, leaves many royal duties in the province specifically assigned to the sovereign's viceroy, the lieutenant governor of New Brunswick, whose direct participation in governance is limited by the conventional stipulations of constitutional monarchy.

The role of the Crown is both legal and practical; it functions in New Brunswick in the same way it does in all of Canada's other provinces, being the centre of a constitutional construct in which the institutions of government acting under the sovereign's authority share the power of the whole. It is thus the foundation of the executive, legislative, and judicial branches of the province's government. The Canadian monarch—since 8 September 2022, King Charles III—is represented and his duties carried out by the lieutenant governor of New Brunswick, whose direct participation in governance is limited by the conventional stipulations of constitutional monarchy, with most related powers entrusted for exercise by the elected parliamentarians, the ministers of the Crown generally drawn from among them, and the judges and justices of the peace. The Crown today primarily functions as a guarantor of continuous and stable governance and a nonpartisan safeguard against the abuse of power.

This arrangement began with the 1867 British North America Act and continued an unbroken line of monarchical government extending back to the early 16th century. However, though it has a separate government headed by the King, as a province, New Brunswick is not itself a kingdom.

Government House in Fredericton is owned by the sovereign only in his capacity as King in right of New Brunswick and used as an official residence by the lieutenant governor and the sovereign, when in New Brunswick.

Those in the royal family perform ceremonial duties when on a tour of the province; the royal persons do not receive any personal income for their service, only the costs associated with the exercise of these obligations are funded by both the Canadian and New Brunswick Crowns in their respective councils. Monuments around New Brunswick mark some of those visits, while others honour a royal personage or event. Further, New Brunswick's monarchical status is illustrated by royal names applied to regions, communities, schools, and buildings, many of which may also have a specific history with a member or members of the royal family; New Brunswick itself is named in honour of King George III, who belonged to the House of Brunswick. Gifts are also sometimes offered from the people of New Brunswick to the royal person to mark a visit or an important milestone; for instance, Queen Elizabeth II was given in 1951 a pair of hand-woven car blankets made by the loom crofters of Gagetown and, in 1976, a quilt hand-sewn by the Havelock United Baptist Church Ladies' Auxiliary.

Associations also exist between the Crown and many private organizations within the province; these may have been founded by a royal charter, received a royal prefix, and/or been honoured with the patronage of a member of the royal family. Examples include the Royal Kennebeccasis Yacht Club, which received its royal prefix from Queen Victoria in 1898. At the various levels of education within New Brunswick, there also exist a number of scholarships and academic awards either established by or named for members of the royal family, such as the Queen Elizabeth II Scholarship, set up by the government of New Brunswick to coincide with the visit of the Queen to the province in 1959.

The main symbol of the monarchy is the sovereign himself, his image (in portrait or effigy) thus being used to signify government authority. A royal cypher or crown may also illustrate the monarchy as the locus of authority, without referring to any specific monarch. Further, though the monarch does not form a part of the constitutions of New Brunswick's honours, they do stem from the Crown as the fount of honour and, so, bear on the insignia symbols of the sovereign.

The modern Crown's place in New Brunswick is a result of its history in the Maritimes region before New Brunswick itself was partitioned from Nova Scotia in 1784 and named for the royal house of King George III, the House of Brunswick-Lüneburg. This administrative split became necessary due to the arrival of some 35,000 to 40,000 United Empire Loyalists, as well as about 3,500 Black Loyalists, fleeing as refugees from the violence directed against them during and after the American Revolution, between 1765 and 1791.