The average temperatures for the year reached 10.5 degree Celsius, a new record high, the DWD said in a statement.
“It was the warmest year in the 138-year temperature records of the national weather service,” the service said.
The number of days when temperatures reached 30 degrees and above also hit a record 20, a day more than in 2003.
The number of summer days — defined as when temperatures are 25 degrees and above — also reached a record 74, 12 more than in 2003.
“Such a hot summer is linked to heightened pressures and therefore health hazards for sensitive people,” the DWD's climate scientist Thomas Deutschlaender warned.
Months of scarce rainfall and hot sunny weather last year had wreaked havoc on crops.
Water traffic including on the Rhine was also crippled as water levels plunged, forcing ship operators to suspend services to keep vessels from running aground.
The extraordinary weather last year had been seized on by many climate activists to push Germany to hold fast to its pledge to slash greenhouse gas emissions by 40 percent by 2020 compared to 1990 levels.
But in its latest annual climate protection report published in June, the government admitted that it was now expecting to achieve 32 percent in reductions compared to 1990.
According to the UN, the last four years were the hottest since global temperature records began, calling it a “clear sign of continuing long-term climate change”.