SR 169 begins at an intersection with SR 164 in downtown Enumclaw, headed north on a road named both 264th Avenue Southeast and Porter Street. The highway passes Thunder Mountain Middle School and crosses Newaukam Creek before exiting Enumclaw. Continuing north, the highway crosses the Green River before passing through the city of Black Diamond. North of Black Diamond, the highway passes to the east of Lake Sawyer before passing through the eastern side of Maple Valley, intersecting SR 516, the Kent Kangley Road. North of Maple Valley the highway parallels, then crosses underneath SR 18 as the highway turns to the northwest, through rural King County. Turning more westerly, the highway passes the Mapplewood Golf and Country Club, before entering southeastern Renton. In Renton, the highway has an interchange with I-405 before terminating just past the freeway at an intersection with SR 900.
Every year the Washington State Department of Transportation (WSDOT) conducts a series of surveys on its highways in the state to measure traffic volume. This is expressed in terms of average annual daily traffic (AADT), which is a measure of traffic volume for any average day of the year. In 2009, WSDOT calculated that as many as 43,000 cars used the highway near Blaine Drive near Renton and as few as 6,600 cars used the highway about 7 mi (11 km) from the southern terminus. The entire highway is listed on the WSDOT List of Highways of Statewide Significance, which marks this portion of the highway as a critical to connecting major communities in the state.