The order was the latest twist in a Belgian's sculptor pursuit to prove that she is the former monarch's daughter.
"I believe that the king will submit to this test, since he has the guarantee that it will remain confidential," Albert's lawyer, Guy Hiernaux, told AFP.
Another lawyer, Alain Berenboom, cautioned that the final decision remains with the monarch.
The court-ordered fine was a major development in a long battle between Albert II and Delphine Boel, who launched proceedings before a top Brussels court in 2013 to have Albert's paternity recognised.
The 81-year-old former monarch, who reigned from 1993 until 2013, has always refused to acknowledge that he could be her father.
Albert refused any test, which led to Thursday's order at the appeals court in Brussels.
The ex-king must now report to an appointed forensic expert who, on the basis of a saliva sample, will carry out a comparative analysis with the DNA of Boel and her mother.
After a request made by Boel, the court said the result of the DNA test would remain secret until the end of the legal proceedings, which could last a year.
"I can't imagine for a second that he (Albert II) doesn't submit to the test," he said.
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