Transportation Between Budapest and Zagreb

Direct buses take 4 to 5 hours. Trains take 6 to 12 hours and longer. So, the bus is faster. Flixbus is fine.

You also could fly from Budapest to Zagreb. www.Skyscanner.com has airfares and schedules.

Flights don’t work well. There are no direct flights from Budapest to Zagreb. Plan on a 3.5-hour trip plus 3+ hours of early arrivals and trips to and from airports. So, 6.5 hours on a plane or 6.5 hours on a direct train. There are some shorter flights, but they have really short changes and that’s just asking for more trouble. For that I take the train.

There is one direct train a day, but who do you buy the ticket from? MAV runs and sells the 6:28 one a day direct train (IC 204 Agram) at pretty good prices (20 euro), but you can’t buy MAV tickets from the US. OBB lists the train but doesn’t sell it and I checked next week till mid-May. I can’t figure out the Croatian site. There are some special summer trains, one of them an overnight train but they don’t start until June (I am pretty sure).

If you want that one direct train you can buy your ticket from MAV the moment you arrive in Europe. The word is that these usually don’t sell out. I've actually been on that train as far as Székesfehérvár and it was pretty empty. Not that means anything.

FlixBus? Some folks like the bus and it’s probably not bad, but not my cup of tea for a day. At least a train you an take a walk and buy a beer.

My solution? You said you were going to Central Europe and the north Balkans, if Vienna is in your plans rearrange the trip to fly out of Vienna to Zagreb, non-stop on Austria Air or Croatian Air for $150 to $300 depending on the day and the flight.

Or rearrange your plans in the north Balkans where you can begin in Zadar on 2 June because there are Ryan Air flights from Budapest to Zadar that starts on that date for about $45.

I took the direct train. It was an older train in July 2016 and the air conditioning was not working inside the compartments for some of the trip. I remember standing in the corridor to get cooler air. An air conditioned bus might have been more comfortable. However, it shouldn't be as hot in May, the older trains may have been replaced by now, and the trip wasn't actually as unpleasant as it may sound.

As an aside, I mainly remember drama at the Hungary-Croatian border crossing where several young people were forced off the train in tears and arguments while their friends were freaking out.. Croatia was not in Schengen at the time and, from what I gathered, several travelers unaccustomed to serious border checks were traveling without passports. (edited, meant Croatia not Czech)

Here is the train and it appeard to br fairly nee IC carriages. That was my experience on the short segment i rode.
https://youtu.be/efH4DL8cze0?si=wjoHrnyw3BQc6imI.

Here is the Bus
https://youtu.be/qKtmH4vW6Yo?si=IzqvCPgUvFi37wBI

And the Balkans tend to be cool and wet in May.

Wait, I just used my US IP to book a ticket to Vienna tomorrow and the direct train to Zagreb two days from now.

Two days ago the MAV site would not even open. Maybe MAV has reopened to the world?

Thanks for the input. We are considering our options now. Initial research leans toward FlixBus but we'll see.

If you do the Flixbus you get a few options for where to get off in Budapest. The first stop is Kelenföld which is a train station. Thats where I would get off. Cheaper ticket and I think even with the metro into town, faster. I have no idea where you are staying but Kelenföld from the bus to the metro station, then a tram and a walk is less than 45 min to the Opera and you get to do some sightseeing along the way. So about 5.6 hours total.

And the Flixbus stop is also the stop before the end stop for the train. Which stop you go to on the train depends on where you are staying.