Sandberg, 50, posted a picture of her and Tom Bernthal, the co-founder and chief executive officer of consulting firm Kelton Global, on her Instagram and Facebook profiles.
Among the first to congratulate was Facebook Chief Executive Officer and long-time friend Mark Zuckerberg.
“Congrats! You’re wonderful for each other and I’m so happy for both of you,” Zuckerberg wrote.
Sandberg lost her husband, Dave Goldberg, who headed SurveyMonkey, in 2015 to a treadmill accident.
The couple, who were married for 11 years, has two children.
Sandberg, one of the most high profile female executives in U.S. business, has authored best-selling books including “Option B”, which is about coping with the sudden death of her husband, and “Lean In: Women, Work, and the Will to Lead”.
Bernthal had previously worked in the White House under President Bill Clinton and for NBC News, where he was an Emmy Award-winning television producer.
(Reporting by Ayanti Bera in Bengaluru; Editing by Sriraj Kalluvila)