From Copenhagen to Amsterdam By Rail

I wish I had the experience to offer you, but thus far, I have only made the calculation for the same journey from Copenhagen to Amsterdam for our upcoming trip in April. This is one bit of advice I got from Morten, in Copenhagen: "Copenhagen to Hamburg is a decent trip by train, but if you are going further than Hamburg then a budget flight will be both cheaper and a lot faster. CPH- Amst or CPH-Paris you should fly." I know I really like the trains in Europe, but ultimately, we chose to reserve a flight for that portion of our journey, to save time and money. We tucked in a train trip in later on. Good luck with your planning, it's part of the fun :)

You can see the options on the Deutsche Bahn website.

The best option appears to be the 7:35 AM departure. There are several different connection options, but the simplest involves just two changes, one in Hamburg and one in Osnabrueck. It gets you to Amsterdam at 7:00 PM.

If you click on "Show details" for a routing, you'll see where the connections take place and how long you'll have to make the change.

Usually there's a lot of money to be saved on long trips like this on fast trains if you buy the ticket early. Or you could fly. In both cases, the low fares are for tickets that are non-refundable and non-changeable.

Any specific Airline? Ryan Air flies that route iirc? It would be doable to arrive in Amsterdam earlier that 7pm, but I'm buying a Eurail Pass, and wouldn't mind staying on the train 11 hours (I love trains!!) I'll check some of the carriers like Norwegian Air, Ryan Air or maybe Icelandic Air

I’m glad to see that my advice is getting re circulated :-)
I Think the general consensus on this forum is that as soon as a train journey is over 5-6 hours, then a flight becomes more competitive in terms of total travel time ( getting to and from the airport, check in etc). But of course this is also a matter if personal preferences. If you are really into trains, then some people on this forum has found the CPH to Hamburg train that goes via the Rødby-Puttgarten ferry very novel, because the train goes onboard the ferry.
If you choose to fly, then I know that Norwegian have good deals on the route, probably SAS as well.

OK, I decided to fly on Norwegian Air Nonstop (the flight is about 1.5 hours) for $59.00 - takes the hassle out of it, and will give me more time in Amsterdam. I'll miss being on the train, getting to see the sights, but I'll have enough of that on other legs of my trip! Thank you Morten!

You’re welcome. With a 1,5 hour flight you are looking at 4 hours, maybe 5 hours max of total travel time from city centre to city centre. That beats a 11 hour train trip in my book, and I really like trains.