Wearing his trademark "hoodie" sweatshirt, jeans and sneakers, the 27-year-old chief executive said he would do the Instagram deal again if he had to, according to attendees at the event.
Hundreds of investors showed up Monday for the presentation at New York's Sheraton Hotel, which was closed to the media.
The world's largest social network aims to raise about $10.6 billion, dwarfing the coming-out parties of tech companies like Google and granting it a market value close to Amazon.com's.
The 8-year-old social network that began as Zuckerberg's Harvard dorm room project indicated an IPO range of $28 to $35 a share Thursday, which would value the company at $77 billion to $96 billion.
The size of the IPO reflects the company's growth and bullish expectations about its money-making potential as a hub for everything from advertising to commerce. Many investors say they expect Facebook to raise its offer price-range as the roadshow progresses from New York to major cities such as Chicago, Boston and San Francisco.
Amid the hoopla of one of the most closely watched IPOs in years are persistent concerns about Facebook's longer-term growth and Zuckerberg's majority control.
Zuckerberg, who will have
Asked about the deal by an attendee at the event, Zuckerberg said Facebook's management had discussed a possible Instagram acquisition at length in several meetings. Facebook decided to act when it saw Instagram's user data cross a "tipping point" from which they believed it would grow significantly, he said.
He said Facebook moved quickly to strike a deal when it became clear that Instagram was open to being acquired.
Zuckerberg was accompanied by finance chief David Ebersman, who was wearing a suit and tie, and Chief Operating Officer Sheryl Sandberg. Investors managed to ask five questions during the event Monday, including a query about Facebook's potential plans to enter China, the world's largest Internet market by users.
Zuckerberg noted that Facebook was blocked in China - a situation experienced by several popular U.S. websites such as YouTube and Twitter.
Sandberg added that the company would be willing to sit down with Chinese government officials and discuss partnerships in the country.
Facebook's emergence as a cultural phenomenon whose beginnings were depicted in the fictionalized 2010 film "The Social Network" added a palpable level of energy and buzz to Monday's event.
One investor was overheard joking that the event should have been held in New York's Madison Square Garden, home of the Knicks basketball team and a standard venue for rock concerts.
Investors had formed a line outside the Sheraton Hotel about an hour before the roadshow started Monday morning, as a nearby media throng awaited the arrival of Facebook executives and elicited inquiries from curious passers-by.
"This is unlike anything we've ever seen," said another investor who was at the event.
Morgan Stanley banker Michael Grimes took the stage to begin the formal presentation as the audience of investors lunched on Cobb salad, ice tea and cookies, attendees said.
With 900 million users, Facebook is challenging established Web businesses such as Google and Yahoo for consumers' online time and advertising dollars.
Susquehanna Financial analyst Herman Leung said in a note to investors Monday that he expected Facebook's revenue to grow 40 percent this year and 33 percent in 2013.
He said the $28 to $35 range for Facebook shares was an "attractive" valuation that provided a "compelling entry point" for investors.
In a separate note published Sunday, Pivotal Research analyst Brian Wieser put a $30 price target on shares of Facebook.
"Our conversations with investors to date suggest that concerns around revenue growth and the absence of mobile monetization will linger for some time," Wieser said.
But, he added, "we would not be surprised if the stock trades up above the IPO price on retail interest in the company over the near term."