Online-accommodation rental service Airbnb Inc. is in discussions with venture capitalist Peter Thiel about a roughly $150 million investment that would value the start-up at around $2.5 billion, according to people familiar with the matter.

The sum nearly doubles the level reached last year, when the San Francisco-based company raised $120 million at a $1.3 billion valuation.

The terms of a deal are still in flux. Some existing Airbnb investors, including venture firms Andreessen Horowitz and Sequoia Capital, are also expected to participate in the round, these people said.