SR 3 begins at a diamond interchange with US 101 south of Shelton in unincorporated Mason County on the Olympic Peninsula.

[3] The highway travels north into Shelton at the end of Oakland Bay on 1st Street and crosses over a Puget Sound and Pacific Railroad line and Goldsborough Creek.

[4] SR 3 turns east on Pine Street and leaves Shelton, traveling northeast along Oakland Bay and a US Navy rail line.

[5] The highway continues northeast past Bremerton National Airport towards the community of Gorst in Kitsap County, where it forms the western terminus of SR 16.

[8] The freeway continues through western Bremerton past the diamond interchange with SR 310 and the community of Chico along Dyes Inlet.

A branch of PSH 14, named SSH 14A, was designated on a gravel road that connected the main highway at Belfair to US 101 in Shelton.

The new interchange, opened in November 2007, split the western terminus of SR 303 between two exits, signed as 45A and 45B,[1] and removed a loop ramp that created turning conflicts.

[39] The project was revived later in the decade and is scheduled to be completed by 2026, carrying the new alignment of SR 3 while the existing road remains as a business route through Belfair.