"Therefore the accused will remain under custody of the ICC pending the final decision on the appeal."
Lubanga is accused of enlisting and conscripting children aged under 15 for his Union of Congolese Patroits, to kill members of a rival tribe in the 1998-2003 war in the Democratic Republic of Congo.
He has pleaded not guilty and described himself as a politician, not a warlord.
Lubanga had insisted he could not flee if released as he has no travel documents and pledged to remain "at the disposal of the court" throughout the appeal.
Lubanga's trial, the ICC's first, was initially to have started in June 2008 but was stalled until the following year when the court ruled that prosecutors had wrongly withheld evidence potentially favourable to his defence.