Montenegro hosted the Netherlands in a friendly on Friday and hammered them, 89-43.
The Balkan team took command from the start, outscoring the Dutch 28-11.
The Netherlands fought back and reduced the arrears to 44-34 by half-time but Montenegro's defensive pressure was too much for the Oranje after the break.
Montenegro, who are coached by Dejan Radonjic, finished seventh at last year's U20 European Championship in Greece while the Netherlands competed in Division B and finished first to clinch promotion.
At the U20 European Championship, which tips off on July 8 in Croatia, Montenegro will compete in Group B against Turkey, Lithuania and Serbia.
Those games will be played in Crikvenica and Montenegro's opening game is against Lithuania.
The Netherlands will be in Group C with Italy, France and Russia.
The clashes with be in Makarska and the Netherlands' first opponents will be the French.