How to Get from Rome to VeniceRome to Venice is a 4 to 6 hour train ride, with the Eurostar Fast train being the fastest and most costly. Trains run between Rome Termini and Venice Santa Lucia train stations but a few trains only go to Mestre station, not into Venice, so if you need to get into Venice be sure to check the final destination.
You'll need to reserve a seat on Rome to Venice trains. Most routes don't require a change to get between the two cities. Currently the first train leaves Rome for Venice at 6:50AM and the last at 18:50. There are two later trains that go only to Mestre and require a change of trains and one later train from Roma Tiburtina station that takes almost 7 hours.
You can check current Rome to Venice schedules and ticket prices on the Trenitalia web site. People in the US may find it easier and more convenient to buy tickets ahead of time through Select Italy - go to Select Italy train tickets page to make reservations and buy tickets direct.