The media mogul, who is recovering from perhaps his most difficult year in the business, is posting on Twitter under the handle rupertmurdoch, spokeswoman Daisy Dunlop at News International confirmed Monday.
The account was opened over the New Year's holiday, but many doubted its authenticity because Murdoch, 80, has generally tried to stay out of the spotlight as his media empire comes under increased scrutiny because of widespread phone hacking at his U.K. newspapers.
Murdoch faced harsh questioning in Parliament last summer and may face additional questions from the wide-ranging Leveson Inquiry into media practices later this year, but he makes no mention of these troubles in his tweets, which include the News Corp. chief's New Year's resolutions.
"My resolutions, try to maintain humility and always curiosity," he tweets. "And of course diet!"
Murdoch had attracted more than 46,000 followers by Monday morning, just two days after he started tweeting. His wife Wendi Deng has also started tweeting — she's wendi_deng.
She refers to the setbacks of the last year in her tweets: "A lot of bad things happened in 2011 but I hope in 2012 we can put them all behind us and sail on to a bright future for everyone Wxx."
She also gently reminds fellow tweeters to spell her first name with an "i'' at the end, not a "y."
The Murdochs' entry into the world of Twitter was met with some bemusement and some hostility by its denizens.
John Prescott, former U.K. deputy prime minister, came up with one of the wittier responses to Murdoch's unexpected surfacing at the very public, very popular micro-blogging site.
"Welcome to Twitter," he writes to the mogul, whose reporters were skilled at hacking into telephone messaging systems. "I've left you a Happy New Year message on my voicemail!"
Others express fears that the wealthy Murdoch will buy the Twitter site.
Murdoch also deleted a tweet in which he suggested that Britons might have too many public holidays for a country facing tough times.
At times in his tweets Murdoch sounds bored with his New Year's holiday. He complains that there are "too many people" on the island of St. Bart's, an exclusive Caribbean hideaway.
"Back to work tomorrow," he says. "Enough idling!"
Murdoch also tweets that some of his friends are "frightened" by what he might say.
He also praises Mike Bloomberg, the Republican mayor of New York City, and Rick Santorum, a Republican presidential candidate.
Murdoch tweeted his wishes for a happy new year and said it would probably exceed expectations.
"Happy 2012," he says. "May it be better than all experts predict. Has to be! Must must change everything to create jobs for all, especially young."
His Twitter profile is accompanied by a snapshot showing Murdoch grimacing. He is wearing a casual white T-shirt with a light blue sweater.
Murdoch was forced to close the News of the World last year because of widespread phone hacking at the tabloid. The victims included celebrities, sports stars, and a murdered teenager whose voicemails had been hacked.
The scandal has damaged Murdoch's financial holdings and raised doubts about whether his family can retain control of the company, which has substantial interests in newspapers, magazines, movies, television and book publishing.