A 70-year-old amateur cyclist died after collapsing during the prestigious Cyclassics race in Hamburg on Sunday.
Police told dpa he was resuscitated on the course during the race but later died in hospital.
A minute's silence was held at the start of the German race for UK cycling talent Finlay Tarling, who died on Friday in a crash with a vehicle at the Tour of Portugal.
French rider Paul Magnier won the 29th edition of the men's professional Cyclassics race, taking victory in Hamburg city centre after almost 205 kilometres following the start in the Lower Saxon town of Buxtehude.
The 22-year-old, who prevailed in a thrilling sprint from a large group, had already won three stages at this year's Giro d'Italia.
Dutch rider Mike Teunissen finished second and Australia's Laurence Pithie took third.
Two riders had to abandon the race after a crash, including Australia's Michael Matthews, winner of four Tour de France stages.
This year's Tour third-placed rider, Mexico's Isaac del Toro, also briefly crashed while taking a feed bag but was able to continue.
The Deutschland Tour begins in the south-west of Germany on Wednesday. On Saturday, the Spanish Vuelta starts in Monaco as the last of year's three Grand Tours.