The musical pair have teamed up with Habitat for Humanity to begin the project, for which over $2 million (GBP1.15 million) has been raised so far.
Connick Jr and Marsalis came up with the idea to construct a neighbourhood built around a music centre, where musicians can learn and practice their art.
Connick Jr says, "I had been kind of coming up blank. The problem is so massive, it's hard to know where to begin. As we talked, we both realised we should really stick to what we know, which is music."
Several members of the Will And Grace heart-throb's own band lost their homes as a result of Hurricane Katrina, which damaged the city in August this year (05).
He adds, "There's a ton of musicians who have no place to go."