Dotcom posted a photo of the dapper dog with the caption "My bestman has arrived".
Dotcom said he was determined to make 20 January "filled with joy". Today marks the day, six years ago, police raided the Coatesville mansion he called home.
On January 20 2012, Dotcom and three others were arrested at the infamous mansion by armed police on behalf of the FBI.
The raid was part of a worldwide operation targeting Dotcom's file-sharing business Megaupload.
Dotcom blames the raid on the breakdown of his marriage to former Filipina model, and the mother of his five children, Mona Dotcom.
The pair split in 2012.
Dotcom said he had banished the bad associated with today's date by marrying Donnelly who he refers to as his "wonderwoman".
Dotcom also marked the day by revealing his lawyers were serving "a multibillion-dollar damages claim" against the New Zealand Government.
"Getting married and getting justice. What a wonderful day." he tweeted.
"Today, 6 years ago, the NZ Govt enabled the unlawful destruction of Megaupload and seizure of my global assets.
"I was arrested for the alleged online piracy of my users. Not even a crime in NZ. My lawyers have served a multi-billion dollar damages claim against the Govt today."
Kim Dotcom and Donnelly, who is 21 years younger than the internet mogul, have been together for two years.
In an earlier interview, Dotcom said: “I’m in love. We’re in love. This is not some fling - this is serious.”
