It is in the Talysh Mountains, a northwestern subrange of the Alborz (Elburz) mountain range.
It is located about 286 km to the south from Baku and 76 km to the south-west from Masallı.
“Caucasian calendar” of 1915, 145 people, mainly the Azerbaijanis shown in the calendar as Tatars, lived in Yardimli village of Lankaran Uyezd of Baku Governorate.
According to a census of 1979, 3114 people and according to a census of 1989,3438 people lived in Yardimli. According to a census of 2010, the city’s population consists of 6700 people.
During the Soviet times it had a status of township. At those times, a carpet-weaving factory, which doesn’t work at present, functioned in Yardimli. There is a museum, mosque and military memorial in the city.
Rayon was founded in 1930. The name remained as Vergedüz Rayonu ( Azerbaijani : Vərgədüz rayonu) until 1938 .
The highest mountains are Şinunkelek Mountain (2419 m) ( Azerbaijani : Shununk Mountain) and Taraken Mountain (2350 m) ( Azerbaijani Mountain: Tarakən Mountain).
According to the official dated January 1, 2013, the rayon population is 61,527.