A story appeared in an American magazine this week accusing Jionni of flirting with a woman he met in Fort Lauderdale, Florida in March last year.
The woman claimed she flirted and danced with Jionni at a club and he later texted her and pursued her and was "ready to cheat" but she turned him down.
Outspoken Snooki, however, doesn't believe it.
She tweeted: "FYI, this BS story is a lie and "told" LAST summer LOL… My man ain't going nowhere #shady."
Meanwhile, Jionni laughed off the claim by joking: "S**t! Nicole hooked up with Brad Pitt last night! How much can I get for that story??"
Snooki - real name Nicole Polizzi - and Jionni married in November at a ceremony held in New Jersey. They'd been engaged since March 2012.
The couple have two children: Lorenzo, two, and Giovanna, four months.
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