The primary law enforcement office for Onslow County is the office of the Sheriff. Historically the office of Sheriff evolved out of the shire reeve, an official responsible for a shire or small division of land. This official position dated to medieval England and transferred to the United States with colonization. Today the Sheriff is an elected official responsible for policing unincorporated areas, maintaining the jail, providing security for the court and school system, serving court papers, and maintaining civil law.

Initially, Onslow Precinct had the position of Provost Marshal, but those chosen frequently refused the office due to a lack of income associated with the title. In 1739 the Colonial Assembly created the office of Sheriff, and during the Colonial era, the Sheriff became the court's most crucial executive and administrative officer. Appointed by the governor after being nominated by the Justices of the Peace, the Sheriff’s responsibilities included tax collection, execution of laws, and supervision of elections. With so much power, especially in tax collection, many Sheriffs in colonial North Carolina were corrupt. Onslow County seems to have a relatively corruption-free history when examining the Sheriff’s office. The one exception is Enoch Ward, who was removed from office by the Governor in 1763 due to complaints about his misconduct.

The colonial assembly created the office of constable, which was the most basic rank of colonial peacekeeping. They supported the Sheriff with the responsibility for law enforcement, preventing breaches of the peace, and punishing those who did break the peace. They served warrants, helped bring civil matters before the court, raised juries, and collected taxes. Today’s position of deputy sheriff serves a similar function as a law enforcement officer and keeper of the peace. Deputies also provide security to the court system as bailiffs and school system as School Resource Officers. Deputies patrol the 767 square miles that makeup Onslow County in twelve-hour shifts, twenty-four hours a day, twelve days a week.

The Sheriff's Office now boasts over 300 members, consisting of civilian support staff, deputies, and detention officers. Various divisions and units make up the Sheriff's Office and assist the Sheriff in carrying out their responsibilities.