Josh Elman has been a project manager with some of Silicon Valley’s hottest companies, including Facebook, Twitter and LinkedIn (LNKD). Now he’s becoming a venture capitalist.

Fortune has learned that Elman will become a principal with Greylock Partners, a firm that is no stranger to LinkedIn vets. It recently added both Adam Nash (ex-VP of product development) and D.J. Patil (ex-chief scientist). LinkedIn founder and ex-CEO Reid Hoffman joined a partner in 2009, and now runs the firm’s seed-stage investing program.

Greylock also was one of LinkedIn’s earliest investors, with more than a 15% ownership stake prior to this past summer’s IPO.

Elman most recently spent two years with Twitter, where he founded and led the micro-messaging company’s “onboarding and growth” team. Before that he was product manager for Facebook Platforms, where he helped launch Facebook Connect. His LinkedIn career spanned January 2004 to July 2005, where he managed product development for LinkedIn Jobs.

Elman also served in product development roles with Zazzle, RealNetworks and Homestead.

Greylock has not yet responded to a request for comment.

Update: I just got off the phone with Elman, who says he doesn’t yet know if he’ll focus on seed-stage investing or on more mature companies. More:

“I’ve managed to work with a bunch of awesome companies that have big visions, and after leaving Twitter began to think maybe there was a role for me in VC where I could apply some of my skills to help the next generation of companies grow… I’ve known Reid Hoffman since 2004 when I was one of the first 20 employees at LinkedIn, and it’s really rare to find a firm where you’ve already worked hands on with some of the people there…”

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