In an updated travel advisory after the bombings and shootings that killed 44 people, the German Foreign Ministry said "political tensions as well as violent clashes and terrorist attacks must still be expected" in Turkey.
"Travellers to Istanbul, Ankara and other major cities in Turkey are urged to exercise heightened vigilance," it said on its website.
"This applies in particular to public places and tourist attractions and generally to large groups of people and public transportation."
Turkish authorities have blamed Isis jihadists for Tuesday's assault on Ataturk airport and identified a Russian, an Uzbek and a Kyrgyz national as the alleged bombers.
Nineteen foreigners were among the dead, with more than 200 people injured.
Germany had already warned its citizens to avoid crowds and tourist sites in Turkey in January after an attack in the heart of Istanbul claimed the lives of 12 of its nationals.