Train from Rome to Venice

The big IF , is the flight arriving on, or very nearly, on time, then what you propose is reasonable

Pre-booking the ticket does result in a lower price , but it locks you into THAT train, and refunds/exchanges usually are not permitted. The price difference does not look huge, so I would be inclined to buy when I got there

While not zero, the chance of trains being sold out is small.

My $0.02

It’s a bit risky
If your flight is exactly on time you MIGHT make that train
It’s a little too tight for my comfort
Will you have to retrieve bags?
I doubt all trains to Venice will be sold out so waiting til you land you just have to pay full price.
If you have the trains apps you could purchase as soon as you land

Or you could spend first night in Rome near the station and head to Venice early am on a discounted ticket

I just booked 1 night with bkft at Hotel Sonya for 135 euros- short walk from Termini

Is it a good idea to pre-book our train tickets from Rome to Venice?

No, it isn't. While trains rarely sell out (why should they?), even full price "BASE" tickets are wasted one hour after the departure of the booked train and, anyway, nobody purchases in advance full price tickets.
Trenitalia has already published the schedules for June 4, buying at the airport station on the day you'd pay 92 Euro per person from Rome Termini to Venice. Plus 14 Euro for the airport train, but that price is fixed and airport trains can't sell out.
If you purchased now, I guess you'd get a discounted SuperEconomy ticket at € 64.9 per person. No changes, no refunds: If you arrive at the track one minute after the train departure, you have wasted € 64.9.
Are you willing to take the risk of wasting that money? How many tickets are going to buy?
More, if you arrive earlier than expected, you can't get on an earlier train. Including the direct FCO-Venice trains that departs from the airport station at 12:36 and at 14:35. Another risk to be considered.

Thank you all for your input. I am not concerned about saving a few dollars by pre-booking. I was just concerned about the availability of the trains and wanted to be sure we would be able to get one that afternoon. Having never travelled by train in Europe (or Canada for that matter) - I just wasn't sure what the best option was. Thanks Again!

Both Trenitalia and Italo serve that route, with numerous departures per day, so the chance of the trains all being sold out is about nil. Although I will note that Italo has no trains between 12:55 and 17;00 or so.

Are you considering taking a train that runs from Rome’s airport (FCO) to Venice! They appear to run frequently to Venice Santa Lucia. Some go to Venice Mestre. You could be well on your way before 3 PM if you consider this option. If you choose to go into Rome first (RomaTermini) you should plan on a 30 minute transfer time by direct train or taxi or closer to an hour by bus or a connecting train. There is a direct train to Venice Santa Lucia that leaves at 13:53 and arrives at 18:34 from the airport.

June 4 is a Saturday. On February 26, Make a search for trains departing in the next few hours (Italian Time is GMT +1) from "Fiumicino Aeroporto" to "Venezia S. Lucia" (or to "Venezia Mestre" if you are staying on the mainland).

The possibility of having all Freccia train seats sold out on any given day is zero.

Very very rarely, I've experienced arriving at the station and the very first Freccia train to Rome/Florence/Venice after my arrival at the station had sold out all seats in standard (formerly known as 2nd) class. In those circumstances I either bought the ticket on the same train at the higher price in premium class (+15%) or business class (+30%) or simply waited for the next train half hour or one hour later, which invariably always had availability in all classes of seats.

There is a fast train from Rome to Venice every hour. The standard class (the cheapest) if sells out (rarely) is likely to sell out for the morning trains, but since you land at around noon, the possibility that a train in the midday hours is full and the standard class is sold out, is really remote. In any case, in the unlikely even that happens, just take the next train an hour later if you don't want to pay the extra 15% or 30% for the more expensive class (which will certainly be available)..

Thank you! I would prefer to go direct from the Airport to St. Lucia Station in Venice if that is an option. Still trying to navigate the searches. I was sure I read that we could go direct from the airport but then other searches I saw and some previous comments I had received on Facebook implied to me that I had to go through Rome's Main terminal. Glad to hear this is in fact an option. We really just want to go straight from the Airport to Venice efficiently as possible. We will be back in Rome two weeks later so we will see the sights then.

Yes, we don't mind paying for first class to get a seat - so I am glad to hear that it should not pose any problems.

if that is an option.

Yes, it is. As I wrote above there are 2 direct trains from FCO to Venice that depart after 12.

Note that direct does not mean "no stop". These trains will make two stops in Rome, then they will keep going north, stopping in Florence, Bologna, Venezia Mestre and, finally, at Venezia S. Lucia station.

On the Off chance that all Trenitalia 2nd class tickets are sold out on June 4, you'd better take a train from FCO to Roma Termini. Once you are there, walk to Italotreno's lounge and buy a 2nd class ticket to Venice. Or install Italotreno's app on your phone and get 2 tickets online at the airport station.

When searching on Trenitalia you need to use the correct Italian station names
Fiumicino
Venezia Santa Lucia

https://www.trenitalia.com/content/tcom/en.html

Also be sure to set the hour back to 00:00 or at least an early in day hour so you get the full schedule

I like using the Omio app to book train tickets if you don’t already have one. ☺️ Happy travels!!

And how can you be sure that Omio app shows all trains and all fares?

Or that this app complies with Trenitalia's requirements about minimum transfer times between trains? In other words, are you sure that all your connections will be protected?