Organised by Polish journalist and blogger Anna Alboth, the "Civil March for Aleppo" aims to build political pressure to help civilians caught up in the Syrian conflict.
Carrying white flags and hiking backpacks and wearing outdoor gear against the cold and wet December weather, the marchers had on Monday left from the centre of the German capital.
Alboth told Germany's left-leaning Tageszeitung daily that only a core group of 30 activists planned to walk all the way, adding that she expected they may be blocked at the Turkish border.
The starting point was the disused airfield of the Nazi-era Tempelhof airport, which during the Cold War became the hub for the Berlin airlift and now houses several thousands refugees from Syria, Iraq and other countries.
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The marchers plan to cover around 20 kilometres (12 miles) a day and walk through the Czech Republic, Austria and several western Balkan countries to Turkey - and then on to Syria.
It is the route into Europe that was taken last year by more than a million people, many fleeing battlefields in Syria and elsewhere in the Middle East, with the majority ending up in the top EU economy Germany.
Backed by Russia and Iran, Syrian troops last week retook control of eastern Aleppo, which had been held by disparate rebel groups since mid-2012, after a devastating month-long offensive that caused tens of thousands of people to flee their homes.
Germany has pledged 15 million euros (USD 15.6 million) in aid to pay for medical staff and trauma counsellors for the devastated city, Development Minister Gerd Mueller said.