"Some news: after four years at @twitter, I'm joining @SoFi as VP of Communications and Policy." Prosser tweeted from an unverified account on Thursday.
Prosser confirmed the news of his departure in an emailed statement to Reuters.
Prosser is the second senior Twitter communications executive to exit this week.
Twitter last week reported its slowest revenue growth since going public in 2013 and set a disappointing forecast, fanning concerns that faster growing social media services will make it a niche product.
© Thomson Reuters 2016