The Eighteenth Judicial Circuit was created by the legislature in 1967 and is composed of Brevard and Seminole Counties. Prior to that time, Brevard and Seminole were part of the Ninth Judicial Circuit along with Indian River, Martin, Okeechobee, Orange, Osceola, and St. Lucie Counties. Prior to the organizational change in the court system which occurred in 1972, the Eighteenth Circuit had a variety of courts including the Circuit Court, the Court of Record of Brevard County, the Brevard County Magistrate's Court, County Judge's Courts, Justice of the Peace Courts and a Small Claims Court. Additionally, each municipality had a Municipal Court.

The Circuit Court in Brevard County had jurisdiction to try capital cases and civil actions not cognizable in the County Judge's Court or the Magistrate's Court. In Seminole County the Circuit Court had jurisdiction to try all felony cases, including capital cases, and civil actions not cognizable in the County Court or the Small Claims Court. The Court of Record in Brevard County was a criminal court that tried all criminal cases except capital cases.

The reorganization of the court system in Florida in 1972 caused many of the courts to be abolished and resulted in statewide uniformity. The only trial courts remaining after the reorganization were the Circuit Court and the County Court. The judges of the abolished courts in Brevard County became Circuit Judges.

The population of the Circuit has grown substantially since 1972 due to the influence of the space program in Brevard County and the effects Disney World has had in Seminole County. In 1973, there were 13 Circuit Judges and 5 County Court Judges. Currently, there are 26 Circuit Judges and 17 County Court Judges.

Presently, the County Court has jurisdiction to try criminal cases classified as misdemeanors, civil actions where the amount in controversy is less than $30,000, small claims cases, landlord and tenant disputes and other miscellaneous actions. The Circuit Court is the state trial court of general jurisdiction. It has jurisdiction to try criminal cases which are classified as felonies, including capital cases; civil actions where the amount in controversy is $30,000 or greater and cases which do not traditionally involve juries such as probate of estates, mortgage foreclosures, juvenile cases, injunctions, dissolution of marriage actions and adoptions.

On January 1, 2023, the jurisdiction of county courts will be increased to include claims up to $50,000.00. This will give the circuit courts jurisdiction over any claims where the amount in controversy is in excess of $50,000.00. This law does not impact the jurisdictional limits of small claims court.

The 18th Circuit has a large geographical area with over eighty miles between the main courthouse in Viera (Melbourne) and the Criminal Justice Center in Sanford. There are a total of six courthouses in the circuit with main facilities located at Viera and Sanford.