Lee announced Tuesday that LinkedIn has signed a lease to occupy the entire 26-story structure scheduled to be completed in the city's South of Market neighborhood by 2016.
City officials say the nearly 450,000 square feet of office space could accommodate some 2,500 employees.
Terms of the deal were not released.
Mountain View-based LinkedIn Corp. currently occupies 135,000 square feet in a downtown San Francisco tower and plans to occupy another 87,000 square feet near downtown.
Earlier this month, Salesforce.com signed a $560 million, 15-year lease to occupy a 61-story skyscraper in San Francisco that's expected to be the tallest building on the West Coast when it's completed in 2017.