The move, in which Wojcicki will replace Salar Kamangar, represents the latest change to Google's top properties by Chief Executive Larry Page and comes as Google is striving to turn the popular video portal into a bigger money-maker.
"It's one of the biggest traffic sources on the Internet, so it makes sense to want to try to monetize the best they can," said Needham & Co analyst Kerry Rice.
Google does not disclose YouTube's financial results, though analysts believe the website generates several billions of dollars in annual revenue from video ads and other promotions.
Wojcicki who is a member of Page's inner circle of top managers known as the "L" Team, was most recently senior vice president of Ads and Commerce. She shared the title with Sridhar Ramaswamy, another Google executive.
Wojcicki's new job is effective immediately, according to the source. It was not immediately clear what Kamangar would do. A report in the tech blog The Information, which first reported news of the change, said that Kamangar was expected to remain at Google, perhaps playing a greater role in Google's in-house venture capital arm.
YouTube, the world's No. 1 video website, is moving to add professional-grade video programs to the vast archive of amateur, home-shot videos as it seeks to attract a bigger slice of the estimated $70 billion in spending on US television ads.
"Like Salar, Susan has a healthy disregard for the impossible and is excited about improving YouTube in ways that people will love," Page said in a statement.
The change at YouTube comes nearly a year after Google appointed Sundar Pichai to lead its Android mobile software group, taking over from Andy Rubin, who is now spearheading a secretive group within Google that is developing robots.
Wojcicki has been with Google from its earliest days. Page and co-founder Sergey Brin set up shop in the garage of Wojcicki's Menlo Park, California home in September 1998, around the time they incorporated the company.