Is it possible to be married in the catholic church after being married in Las Vegas?

Almost anything is possible. Are you talking about being re-married to the same person, or do you mean you got drunk and are not even sure you knew the person before your big wedding day and now want to marry another person? Was it a Catholic church in Las Vegas or was it an "Elvis chapel" It's tough to answer a question when the details are so sparse.

Speak with a priest or deacon about this.

wunderin25,
Yes it is possible depending on conditions.
Examples if you and your wife were first marries in a Las Vegas marriage chapel and now want a Christian marriage it is possible.
If you were marries to someone else in Las Vegas and now want to marry a Catholic in The Church it is likely that the first marriage may be considered not a valid Christian marriage, so it is possible to be marries in The Church.
But to be sure about it talk it over with a Catholic Priest and mention all the correct details.
Peace and kindness,
Fred