The report by Reporters Without Borders (RSF) adds to a growing chorus of criticism from Western governments and rights groups of the EU candidate's jailing of journalists, most of whom are kept in pre-trial detention.
Repressive laws, broad and vague legal provisions and a paranoid judiciary were to blame for the high number of arrests, RSF said, and only a complete overhaul of Turkey's anti-terrorism law and other legal articles could change this.
“Turkey is now the world's biggest prison for journalists, a sad paradox for a country that portrays itself as a regional democratic model,” France-based RSF said in a statement.
RSF said a total of 72 media workers were currently in detention, of whom at least 42 journalists and four media assistants were being held because of their work. RSF was still investigating the cases of the remaining detainees.
Turkish Prime Minister Tayyip Erdogan's government says most of the detained media workers are being held for serious crimes, such as membership of an armed terrorist organization, that have nothing to do with journalism.
First elected a decade ago with an overwhelming majority, Erdogan has presided over a period of unprecedented prosperity, winning him admirers among Western nations keen to portray Turkey as an example in a troubled region.
But that narrative has been increasingly undermined by criticism of the authoritarian style of his rule.
Hundreds of politicians and academics are also in jail on charges of plotting against the government, while more than 300 army officers were convicted this year of conspiring against Erdogan almost a decade ago, and handed long jail terms.