SR 123 begins at an intersection with SR 85 north of Northwest Florida Regional Airport to the southwest of Niceville in Okaloosa County, heading north-northeast on two-lane undivided Roger J. Clary Highway.

The road passes through forested areas on the grounds of Eglin Air Force Base, bypassing Niceville to the west.

More than 30,000 drivers travel State Roads 85 and 123 each day between Fort Walton Beach and the suburbs of Niceville, Valparaiso and Crestview, and northern Okaloosa County.

The roads, and their connection to Interstate 10, form an important economic development corridor that supports the tourism industry, Eglin AFB and the Northwest Florida Regional Airport.

In addition, the Florida Department of Transportation (FDOT) is currently designing a similar flyover ramp to better connect S.R.