The blaze sent a huge cloud of smoke over Athens and prompted multiple evacuations near Tatoi, 20 kilometres to the north.
Thousands of people fled their homes north of Athens on Tuesday as a wildfire reached residential areas.
It comes just a day after Prime Minister Kyriakos Mitsotakis said Greece is currently in the midst of its "worst heatwave" in more than 30 years.
The blaze sent a huge cloud of smoke over Athens and prompted multiple evacuations near Tatoi, 20 kilometres to the north. Residents left their homes in cars and on motorcycles, heading toward the capital amid a blanket of smoke.
“It is a large fire and it will take a lot of work to get this under control,” greater Athens regional governor George Patoulis told state-run ERT television. “The foliage is very dense in these areas and it is very dried out due to the heatwave, so the conditions are difficult.”
Wildfires also raged in other parts of Greece, prompting evacuations in a coastal area of the southern Peloponnese region as well as on the islands of Evia and Kos, authorities said.
Mitsotakis said on Monday that the country is "facing the worst heatwave since 1987... [causing] a burden on the electricity network." The 1987 heatwave killed more than 1,100 people.
Mitsotakis added the authorities "were doing everything possible to deal with the situation" and urged users to "limit their consumption especially at the beginning of the afternoon and during the night".
Temperatures reached 45°C in some regions on Monday with the heatwave expected to peak early this week.
The Greek capital saw highs of 42°C in some parts on Tuesday. Authorities have closed ancient sites during afternoon hours, including the Acropolis. The ancient citadel is normally open from 8 a.m. to 8 p.m. in the summer but will have reduced hours through Friday, closing between midday and 5 pm.
Fires that broke out last weekend were in recession on Monday but firefighters continued to work to control them.
"In July we had 1,584 fires against 953 in 2019," said Deputy Minister of Civil Protection Nikos Hardalias on Star TV, estimating that "we are no longer talking about climate change but about a climate threat".
"We are in a phase of absolute climatic deregulation", he also said on public television ERT, specifying that "in the last 48 hours, we have had 116 fires" in Greece.
Meanwhile, at least eight people have died in Turkey as wildfires spread in the touristic Southern part of the country with the European Union and other nations promising water-dropping planes to help.