The outage began at around 6:30 p.m. and, at its peak, affected more than 43,000 customers, according to Seattle City Light.
City Light officials blamed the outage on a breaker failure within a substation, but they don't yet know exactly what happened.
The outage affected parts of the University District, Ravenna, Wedgweood, Greenlake and Lake City.
Traffic was backed up in several neighborhoods because traffic lights went out. Mika Chapman was on a bus, but decided to walk home rather than sit on a stationary bus.
"I got tired of sitting on the bus forever," Chapman said. "The bus was barely moving. (The driver) said as soon as we got off the freeway and hit some sidewalk he'd let us off."
By 8 p.m., City Light had restored power to 95 percent of affected customers. Power was fully restored by 9 p.m.