Please be aware that Brussels has multiple airports and that these results are for all airports serving the city.
The best month to fly between Brussels and Amsterdam is June and the most expensive month to fly is December. (Average prices, based on 673 datapoints.)
The best day to arrive at Brussels is Monday and it would be best to avoid Friday, as prices are on average 8.97% higher than on Monday. (Average prices, based on 924 datapoints.)