Is it possible to make last-minute reservations on the City Night Train?

On French railways website, it says international travels could not be booked, and also that the next trains (until Tuesday) are full. But SNCF is not very good with international travels. EDIT: trying to book again, apparently the availability is random. For some trips it works, but not all.

I tried also on loco2 and they show some trains. It is probably bookable but they send tickets to UK only, so not sure if this website is made to use for last minute. EDIT: according to the comment and Jamie post they offer print-at-home options but not on all tickets. So it's worth giving it a try.

So I guess your best chance is to go to a DB office indeed. I remember the same troubles when booking a trip from Munich to Zagreb, the DB ticket machine wouldn't want to print a ticket (it was 1 hour before the departure though). The office was closed at that time but I suppose they would have been able to sell it.

Upon Vince's suggestion I am posting my comment as an answer, this is just from personal experience and I have no facts to back it up with. The last time I tried this was in 2010 while traveling through Europe by rail for a month.

Did you try calling the booking service? Since the international trains can easily be booked from almost any EU country I've had no problem calling the Swedish railway company SJ, DB (Germany) or SNCF (France) and then be able have those tickets sent to my home, picked up at a station or received a booking number that can be printed in the ticket vendor machine. They can also give you concrete information if the train is fully booked or not.

Going to the station is the next best thing, if there is an available ticket they will sell it to you there :D

Most tickets sold from bahn.de are print at home tickets (called Online-Tickets by the German Railways) and can be bought until shortly before departure.

The Online-Tickets are however not accepted in all trains, especially international trains, e.g. the CityNightLine trains to France. If you want to order a ticket on bahn.de for an itinerary with at least one train where Online-Tickets are not accepted, the tickets are sent you by mail and therefore such tickets must be ordered at least three (working) days in advance.

If it is too late to buy your CNL ticket from bahn.de, you can still buy the ticket from a DB ticket automat, a DB ticket shop (Reisezentrum) or in the train (probably with an additional fee).

When this question was originally asked (September 21st 2012), it was not possible to make a last-minute reservation on the Deutsche Bahn site. However I have just checked again (8th January 2013), and it is now possible.

It should also be possible to book a CNL train three days in advance or less at Voyages-SNCF.com. I have just tried for a date in three days time and I can proceed to the payment page. My understanding of the Resarail system that powers the voyages-sncf site, is that it would not be possible to get to this page if it was not possible to book. The ticket delivery options involve picking up the ticket with your credit card at the station.

At Loco2 we currently use a system called Euronet, which is owned by SNCF and connected to Resarail, so tickets, prices and availability are the same, but there are sometimes differences in ticket delivery options, as seems to be the case with this journey. We can only offer posted tickets for this journey, meaning that they are only available to UK customers booking more than 10 days in advance. We will soon have the same ticket delivery options as Voyages-SNCF soon.

One more thing to note is that the CNL services are "Subject to compulsory reservation", which I think means that if the train is sold out then it is not possible to buy a ticket on the day (unlike lots of trains where you can buy a ticket without a reservation regardless of how many other tickets have been sold). I guess in general this is a good thing because it wouldn't be very nice to not have a seat or a bed for the whole night on a train!