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 July. (Average prices, based on 230 datapoints.)
The best day to arrive at Brussels is Friday and it would be best to avoid Saturday, as prices are on average 41.41% higher than on Friday. (Average prices, based on 230 datapoints.)