More than 500 firefighters battled the blaze on the lower slopes of Mount Parnitha, assisted by nine helicopters, seven aircraft and hundreds of police in a densely vegetated area in the suburbs of Varympopi and Adames, some 20 km north of central Athens.
Temperatures of more than 104 Fahrenheit and winds have fanned wildfires in different areas of Greece in recent days.
On Tuesday, some places recorded temperatures of over 115 Fahrenheit.
The blaze north of Athens had three main fronts at the suburbs of Varympopi, Adames and Thrakomakedones, scorching homes and cars and forcing residents to flee.
On Wednesday morning, helicopters dropped water to try and contain fires spreading near an industrial area outside Athens.
Europe is grappling with a summer of extreme weather, from heavy flooding in the north to the severe heatwaves and fires that have engulfed several areas in the Mediterranean region.