This is the first time that members of Blood & Honour have been convicted on the basis on anti-racism legislation.
One of the concerts took place during a ceremony honouring the Nazi's paramilitary organisation, the SS.
One of the concerts was also covertly filmed by VRT News.
One of those convicted also attended a memorial concert in honour of Ian Stuart Donaldson, the English founder of Blood & Honour.
The court ruled that it was established that the three defendants were involved in the organisation of a neo-Nazi ceremony of remembrance and that during the concerts inflammatory and racist language was openly used.
Two of the three defendants received a three month suspended gaol sentence. Given his record the third will have to serve his three month custodial sentence.
Belgium's anti-racism centre CGKR is upbeat. Jozef De Witte (photo): "We're pleased that there is a conviction. It's an important precedent. At last a court has acted and taken account of the spirit of the law."