Train tickets after landing in Madrid to Sevilla

No one can give you a definitive answer. The problem is that the time to get through immigration, and then to Atocha station is impossible to predict with any accuracy. You either buy well ahead and leave a healthy buffer (three hours?, Four hours?) or head to Atocha and hop the first train.

Trains do sell out, depends on the season, day, and even time. There are plenty of trains per day to Seville, you can also get a train to Cordoba (that would be heading to Malaga or other points) and change to regional trains to Seville...so lots of options.

I've often seen trains listed as "Full" on the Renfe website. That seems a lot more common in Spain than in other countries in Europe. This is what I see on the schedule for tomorrow, October 4:

Total departures: 22 (one being a very slow Media Distancia you wouldn't want)

Full trains: 2

Trains with only limited-mobility seats remaining: 6

I don't know what the limited-mobility seating is like; if those are flip-down seats in the area where wheelchairs are usually positioned, they might be rather uncomfortable for a trip taking over 2-1/2 hours.

I took a look at November 2 as well. It's a Saturday, and I don't know whether that makes it more or less likely to end up with a bunch of sold-out trains. At the moment there's just one train with only limited-mobility seating. I see some rather attractive fares still available for that date, which may indicate demand isn't exceptionally high and there won't be many trains filling up. On the other hand, some people might judge the fares low enough to make early purchase worthwhile.

If you buy in advance, you'd probably be smart to opt for an Elige ticket, which allows for one change, for which you just pay any additional fare based on the current price (and there would almost certainly be additional fare due if you buy a ticket soon at the sort of bargain price I'm seeing). There's probably a time-limit for ticket changes; I haven't dug into the details.

I've never bought a train ticket in advance for my day of arrival in Europe, so I can't provide any personal experience, but I've looked at schedules and fares enough to know that you're likely to pay a rather high price if you wait until you arrive to buy the ticket.

Last October, I flew from Paris to Madrid to get to Sevilla. I bought my tickets in August and took a train that departed 3 hours after the scheduled arrival time of the flight. I’d allow four hours if I had to go through passport control at Barajas. I do not wait to buy tickets until after I arrive because I find that stressful and avoiding stress when traveling is job 1 for me. Between worry that the train will be sold out and concern about the possibility of language difficulties at the station, I opt to buy my tickets ahead of time. And the funny thing is that I speak Spanish but I think way too slowly to get anything done in a hurry.

I stopped at the airport train station on my last trip to Spain to purchase a ticket for a future date. Those folks deal with a lot of international visitors, I'm sure. I was far too brain-dead to call on my rusty, minimal Spanish, and I had no problem at all buying what I needed.

I have taken the train to Cordoba, not Seville, upon arrival twice. The first time, tickets were sold out to Seville. So I am one who likes to buy ahead - but like acraven said, I also make the investment into the elige ticket to allow for a change if the plane is late. I also have trip insurance as a back up.

I have a solution. You can book flexible tickets on Iryo from Atocha to Sevilla. https://iryo.eu/en/home

So, for example, there's a 10:35 AM departure from Atocha to Sevilla. The price is 28.36 Euros at this moment for "INICAL" (standard class). That might be cutting it close to make, right? Well, you can pay an extra 5 euros per ticket, click "LARGE SUITCASE AND GREATER FLEXIBILITY FOR CHANGES AND REFUNDS for 5.00 € more."

This extra fee means you can take the next train at 12:55 PM for no charge.

I suppose you run the risk of every single train later in the day being 100% booked so you can't change your ticket, but I think it's unlikely. I will say that intercity trains I've taken in Spain are pretty often 98-100% full.

Another solution is Renfe’s new ticket feature which solves the problem of buying an unchangeable/nonrefundable train ticket that you might be unable to use if you are delayed getting from the airport to the train station. You can now buy the least expensive Renfe ticket and pay for the “ELIGE”or “ELIGE CONFORT” upgrade which makes it possible to change the ticket one time at no charge. Mid-morning on a Saturday should be fast in a taxi. If you’re out of the airport after one hour, you probably could be at Atocha in 35 minutes. And if not— you can just change the train ticket at the airport to the next train. The change of ticket to another train is subject to seats being available on the new train.
If you are delayed to the point that it’s not possible to make the train you’re ticketed on— you can simply change your Renfe train ticket to a later train traveling from Madrid Atocha to Sevilla Santa Justa train stations.
The ELiGE supplement varies; usually its about €10
Renfe has AVE trains departing Madrid Atocha for Seville on November 2 at 11:05 and 11:53am. IRYO has a train at 12:55pm. Between Iryo and Renfe there are at least two trains every hour until 2pm.
Friday November 1 is All Saint’s Day— a national holiday in Spain. That makes it a good idea to book your train online as soon as possible.

Have a great time in Spain!

www.Renfe.com
www.IRYO.eu
www.TheTrainline.com