Travellers have a choice of very different trains when heading from Amsterdam to the Belgian capital

When travelling by train from Amsterdam to Bruxelles, you can take these Eurostar (formerly Thalys) trains, or the alternative slower, InterCity trains.

Two big ticks in the box from taking these trains:

(1) Despite being faster, the most heavily discounted tickets, tend to be no more expensive than for the InterCity trains

(2) Tickets include a seat reservation

Taking these Eurostar (formerly Thalys) trains:

Final Destination: Paris Nord or Brussel-Zuid

All trains also call at: Schiphol; Rotterdam; Antwerpen

Note that these Thalys (and Eurostar) trains do not call at Bruxelles Nord or Bruxelles Central, but the alternative (slower) InterCity Brussels trains do call at those stations.

The Eurostar trains:

The Eurostar trains from Amsterdam to London call at Bruxelles-Midi/Brussel-Zuid station and tickets can be booked for journeys by Eurostar between these cities, so they have been included in the frequency total.

When looking up tickets for this journey, keep in mind that these Eurostar (formerly Thalys) trains don't arrive at the central station in Bruxelles/Brussels.
Therefore when a ticket service offers a selection of arrival stations in the city, choose the Midi station, or the 'South' station.

Book early and save: Yes

Online bookings open: up to 6 months ahead of the travel date

This booking period tends to be shorter when looking up journeys between mid August and mid October.

Though take care if you will be looking up a journey more than six months ahead of the travel date.
For a few weeks after the six month period the discounted ticket prices can also be available, but the non-discounted tickets can be on sale for dates further ahead.
So if you be will looking up a journey more than six months ahead and only see prices of more than €100, refrain from purchasing and return to the booking service a few weeks later.

Trains departing at different times can be cheaper than others leaving on the same day, so you may need to look through the day's departures to find the cheapest fares.

Seats will automatically be assigned when booking tickets for this journey.

The limited numbers of cheapest discounted tickets for the Eurostar (formerly Thalys) trains are similarly priced to the tickets for the, alternative slower InterCity Brussels trains. 
So when you're booking ahead, you can get to Bruxelles/Brussels faster, in a reserved seat - and it won't cost you any more.

Though when the cheapest Eurostar (formerly Thalys) tickets have sold out, you can save money by taking those InterCity trains.

*Exchanges

Book to travel in Standard and Eurostar Plus class:
The booked date and time can be exchanged to a different departure to the same destination up to one hour before departure time.

• If the cost of your new ticket is more than the cost of your original ticket, you will be required to pay the difference;
• If the cost of your new ticket is less than the cost of your original ticket, you will not receive a refund of the difference.

Book to travel in Eurostar Premier class:
The booked date and time can be exchanged to a different departure to the same destination up to 48hrs after departure time (from November 4th 2024).

• If the cost of your new ticket is more than the cost of your original ticket, you will be required to pay the difference;
• If the cost of your new ticket is less than the cost of your original ticket, you will not receive a refund of the difference.

The Eurostar ticket terms summary is here

Refunds

Book to travel in Standard and Eurostar Plus class:

• Up to seven days or more before the date of departure you will need to pay a fee of £25 per person for a one-way / single ticket and £50 per person for a two-way / return ticket - So you will only receive any sum you paid in excess of these sums.
• Less than seven days before the date of departure, tickets are non-refundable - Also applies if you exchanged a ticket to an alternative departure, under seven days ahead.

Book to travel in Premier class:
Up until 48hrs after departure time (from November 4th 2024), tickets can be refunded at no additional cost,

The Eurostar ticket terms summary is here

Child tickets
Children under the age of 12 travel at a flat rate price of €15 in Standard, €20 in Comfort and €30 in Premium Class.
Source = Eurostar

Bike Tickets

Tickets are not-required as non-folding bikes can only be taken on board as hand luggage - as both wheels must be removed and everything must be covered by a non-rigid cover with maximum dimensions of 135 x 85 x 30 cm.

Dog Tickets

Charged at a flat fee rate of €30, but the payment will be taken by the train conductor, as these tickets cannot be booked online.

Rail Pass Users:

Rail Pass users will need to be pay a reservation fee prior to boarding.

Reservation fees do not apply on the alternative IC trains, so if you will be making this journey with an InterRail or Eurail Pass, you'll save more than €15 if you avoid these Thalys trains.

Final Destination: Bruxelles-Midi/Brussel-Zuid

All trains also call at: Schiphol Airport; Rotterdam; Antwerpen; Mechelen; Brussels Airport, Bruxelles Nord.

These Intercity trains from Amsterdam to Bruxelles are slower than the alternative high speed train, but here are four reasons why taking the Intercity can be an option worth considering:

(1) When the most heavily discounted tickets for the faster trains have sold out, these Intercity trains become the (much) cheaper option.
If you want to book last minute tickets at the station, you can save more than €20 by taking these trains.

(2) Book in advance and the tickets will be date, but not train specific so you can hop on any train on your travel date (book the cheapest Eurostar (formerly Thalys) ticket and you'll be committed to travelling by a specific departure).

(3) If you will be travelling with a rail pass, you can avoid the comparatively expensive rail pass reservation fees, that are charged on the alternative Thalys trains.

(4) These IC trains make additional station calls in Bruxelles compared to the Eurostar (formerly Thalys) trains.

Heading to Bruxelles/Brussels city centre:

Note that these InterCity Brussels trains call at Bruxelles-Central station - the most convenient station for the city centre, hence it being the default destination station for this journey summary.

These InterCity trains also call at Bruxelles-Nord station - particularly useful if your final destination is on the Bruxelles 'pre-Metro' tram lines 3 or 4.
If you'll be heading to Bruxelles-Nord from Amsterdam and take the high speed trains, your end-to-end journey will only be around 25 mins faster; and it won't be direct.

In contrast, the only station in the city that the alternative Eurostar (formerly Thalys) trains call at is Bruxelles-Midi Brussel-Zuid - which is the station in Bruxelles that these InterCity trains terminate at.
Brussel-Zuid lives up to its name because it is located to the south of the city centre.

Book early and save: Yes

Online bookings open: 6 months ahead* of the travel date - USUALLY

These Intercity Brussels trains are slower, but typically cheaper; though if you're booking more than a couple of weeks ahead, the price difference between the two services can be less than €5.

However, when the discounted tickets for the Eurostar (formerly Thalys) trains are sold out, these InterCity Brussels trains are the cheapest option
So, if you will be booking tickets on your day of travel, these InterCity trains will be (much) cheaper than the Thalys trains

If you want to take one of these DIRECT InterCity trains,  look for the trains that have '0' changes and only 'IC Brussels' shown by the journey.

Rail pass users:

Take these Intercity trains and  you can avoid the comparatively expensive rail pass reservation fees that are charged on the Thalys trains.