The court rejected a claim from a family in the North Rhine-Westphalian city of Gelsenkirchen, who had applied for extra benefits for their seriously disabled, six-year-old son.
Under the Hartz IV system, the long-term unemployed receive payments for their children as well as themselves.
However, the court ruled that higher benefit rates given to disabled adults did not apply to children aged under 15.
In addition, the family could not claim the hardship regulations previously proposed by Germany's Constitutional Court in February.
The youngest son of the family of four, which cannot live solely on the salary earned by the father and therefore receives a supplementary Hartz IV benefit, suffers from physical and intellectual development problems, as well as asthma. He also has limited mobility.
The boy was acknowledged as seriously disabled in March 2007, when he was three, at which point his parents applied for a special additional payment for disabled people.
People receiving this extra payment get 17 percent more money – which for an adolescent, would work out to about €35 a month.
But the job centre in Gelsenkirchen refused the payment increase. And on Thursday Germany's highest social court agreed with that decision.
The extra payment was available only to needy adults, who because of illness or disability could not work. Children under 15 were not fit for work – and therefore were not eligible, the court ruled.