Police in Athens on Friday said they had arrested a Greek couple suspected of having purchased a Roma baby for 4,000 euros ($5,500).
The couple, a 53-year-old man and his 48-year-old wife, told police that they had received the baby girl, then only a few weeks old, from a Roma woman in March.
The woman then unsuccessfully tried to register the baby as her own child.
Private adoption is legal in Greece as long as money is not exchanged in the process.
The case came amid heightened scrutiny by Greek authorities after the discovery of a mysterious blonde girl living in a Roma camp with a couple who were accused of abducting her.
Greece's supreme court has ordered a general review of newborn registrations after the discovery of the blonde girl known as Maria exposed lax recording practices around the country permitting the misuse of state benefits.
Maria's false parents, who were arrested last week, are believed to have declared a total of 14 children to claim increased family support benefits.
Maria is thought to be Bulgarian, and left behind in the Greek Roma camp by her biological mother who could not care for her.
Bulgarian authorities on Thursday questioned a Roma couple thought to be the girl's biological parents. The result of DNA tests to confirm the girl's parentage are expected next month.