Cumhuriyet's former editor-in-chief, Can Dundar, fled to Germany earlier this year while appealing against a prison term
"Our work is hard, the pressure is great, the threat is serious. But nothing will stop us," the opposition paper said in an article published as German Foreign Minister Frank-Walter Steinmeier visited Turkey.
Cumhuriyet, which has taken a strong line against President Recep Tayyip Erdogan and his ruling Justice and Development Party, has faced an intensifying crackdown since Turkey's failed coup in July.
Over the past two weeks, police have arrested editor-in-chief Murat Sabuncu, board chairman Akin Atalay and eight other staff members, accusing them of links to Kurdish militant group PKK and the movement of US-based preacher Fethullah Gulen, whom it blames for the attempted coup.
In their guest editorial, the daily's journalists wrote: "We, the citizens of this country, need freedom of speech and the press, which is indispensable for every democratic country."
"The message of our editor-in-chief Murat Sabuncu, which he sent from prison and which filled our eyes with tears, is the principle of everyone who works at Cumhuriyet: We will only bow before our people and our readers."
The editorial was published by 37 German newspapers and their websites, including Spiegel Online, Die Welt, Die Zeit and Sueddeutsche Zeitung.
Developments in Turkey have a strong resonance in Germany, which is home to a three-million-strong ethnic Turkish population, the legacy of a massive "guest worker" programme in the 1960s and 70s.
Cumhuriyet's former editor-in-chief, Can Dundar, fled to Germany earlier this year while appealing against a prison term for revealing state secrets.
Since the coup attempt, more than 100 journalists have been arrested while 170 media outlets including newspapers and broadcasters have been closed down, the Turkey Journalists' Association has said.
Some 35,000 people have been detained and tens of thousands more have lost their jobs -- among them military officers, civil servants, judges and teachers.
The arrests have fuelled tensions between Ankara and the European Union, which has made no secret of its concerns over the scale of the crackdown.
Ahead of his visit, Steinmeier expressed concerns over Erdogan's increasing pressure on Turkey's civil society.
"When the existence of civil society is threatened, then democracy is also threatened," he said, expressing Berlin's desire to help "persecuted scientists, cultural workers, journalists, who can no longer work in Turkey come to Germany to work".