The underpinnings for Oakland’s improving fortunes were set last decade through efforts to expand the urban population, and upon the renovation and reopening of the Fox Theater, a long-shuttered landmark, in 2009, observers say.

But spillover from San Francisco’s tech boom is providing the latest charge as companies and workers look for affordable space, said Jason Volpe, a senior vice president with Jones Lang LaSalle, the commercial real estate brokerage firm.

Downtown Oakland office landlords are asking around $29 a square foot annually, about half the rent for similar space in San Francisco, according to Jones Lang. And amenities nonexistent a few years ago are attracting millennials looking to set up residence. In turn, that is starting to attract employers.

“There are groups being priced out of San Francisco, and for a lot of reasons — access to transit being one and a central location in the Bay Area being another — Oakland is a natural fit,” said Mr. Volpe, who has lived and worked in the Oakland area for the last six years. “The concentration of what I would call highly desirable things to do from a commercial and entertainment standpoint — restaurants, bars, art galleries, live music venues — has done nothing but increase.”

Oakland is drawing office investors as well. This fall, Strada Investment Group of San Francisco made its first foray into Oakland, buying two downtown City Center buildings with Angelo, Gordon & Company of New York as its partner.