The tech giant announced in June it was buying the social media company for $26.2 billion. Gross expects the deal to close in about two months.
LinkedIn is currently trading at slightly more than $192 and Microsoft is paying $196 a share.
While not that's not a big deal, "over two months it's probably a 10 to 11 percent annualized return," the Janus Capital fund manager said in an interview with CNBC's "Power Lunch" on Tuesday.
That said, overall, Gross has been warning about the influence of the central banks on the markets. In his latest letter to investors Tuesday, he said central bankers have turned investing into a casino game with an unpleasant likely outcome.
Gross' $1.5 billion Janus Global Unconstrained Bond Fund has gained just shy of 5 percent this year, putting it in the top third of its peers but slightly behind the 5.8 percent S&P 500 return, according to Morningstar.
Gross told CNBC the fund is producing that return with "very little volatility."
"That's why it's doing well. That's why inflows are coming in. That's why I'm a happy camper today," he said.
— CNBC's Jeff Cox contributed to this report.