The two leaders spoke about the disastrous conditions in central and western Russia via telephone, Merkel's press office said.
Merkel expressed “Germany's solidarity and readiness to help during the devastating fires” to the Russian leader.
Medvedev thanked the chancellor and agreed to have Russian emergency authorities review how German organisations can help.
Details on exactly what kind of aid the chancellor made available were not revealed.
On Wednesday, dangerously thick smoke from the fires reportedly choked the streets of Moscow, reaching all the way through subway lines as fires approached the city.
The country has been suffering its worst heat wave on record, sparking fires that have killed 48 people, according to the Associated Press news agency.
Temperatures have topped out at 38 degrees Celsius in a country where summer heat usually does not exceed 23 degrees, AP said.
Russian authorities advised Moscow residents to take precautions against the smog, which has already been killing off wildlife and pet birds.
Meanwhile thousands of army troops had been deployed to beat back flames from reaching a nuclear research facility in Sarov, the news agency said.