The ex 'Real Housewives of New Jersey' star tells TMZ ... he's known for some time Teresa's been dating Luis Ruelas, and he's happy to see her with someone new. Joe says his ex-wife's equally happy to know he's moving on too.

Teresa revealed her new flame's identity Monday, and sources close to her tell us she met Luis a couple of months ago at the Jersey shore. We're told they're taking things slow ... not living together, but very happy as a couple.

Remember, Joe and Teresa recently finalized their divorce after 20 years of marriage. They'd separated following his prison release and deportation to Italy.

And, get this ... things are going well enough with Luis that Teresa's already introduced him to her 4 daughters with Joe.