The 66-year-old woman had taken the case to the Constitutional Court in Karlsruhe after spending decades uncertain about who her biological father was.
But the court decided that making the man take such a test would be a contravention of his constitutional rights.
It was “a big disappointment” for the woman, her lawyer Paul Kreierhoff said.
The decision means that the right for a child to know about their ancestry remains limited to the right to know whether one's legal father is also one's biological father.
Because the 88-year-old man has never legally acknowledged his fatherhood, he is not legally obliged to undergo a test, the court decided.
With the rejection of her case by Germany's highest court, the woman's last chance of ever finding out who her biological father is now likely gone.
For years the man rejected her appeals to undergo a DNA test, despite the results of such a DNA test having no legal consequences for the man, such paying for child support.