Carrying a normal complement of four, its mission includes firefighting, search and rescue, and response to chemical, biological, radiological, nuclear, and explosive (CBRNE) emergencies.

[4][5][6][7] In the 1970s the United States Maritime Administration funded a special program to train a contingent of 50 Seattle firefighters to provide land-based support in the control and extinguishing of dockside and shipboard conflagrations.

[4][10] Procurement of a modern fireboat to replace Alki was part of a successful public safety levy enacted by Seattle voters in 2003 approving its construction.

[2] The 108-foot (33 m) Leschi is powered by twin diesel engines rated at 1,550 horsepower (1,160 kW), turning 72-inch (1,800 mm) four-blade propellers, which give the ship a flank speed of 14 knots (26 km/h; 16 mph).

[2] By displacement and pump capacity, it is the largest of ten municipal-owned fireboats that support the U.S. Coast Guard's regional marine firefighting plan for Puget Sound.

[2] Leschi is designed to operate with a complement of four personnel, but has a command and communications room for use by senior SFD officers in the event of a catastrophe that renders land facilities unusable.

[11] A thermal imaging camera system allows the ship's crew to locate distressed persons in the water (such as in a man overboard emergency) at night or during other low-visibility conditions.