Expobank, which has its headquarters in Moscow, has a client base of over 250,000 customers using 32 branches across western Russia.
If all goes to schedule, the deal should be completed by this summer and will be Barclays' first foray into Russian retail banking, a market the bank has been keen to tap for some time.
The Russian bank has assets of around $1.24 billion, according to Bloomberg, and employs1,300 people, making it one of Russia's 50 biggest banks in size.
Frits Seegers, chief executive of Barclays' global retail and commercial banking arm, said: "Expobank is a well-run bank with a good track record of innovative distribution and represents a great opportunity for Barclays.
"Its existing relationships and infrastructure create the ideal platform for us to become one of the leading retail and commercial banks in Russia, one of the world's fastest growing economies and a market we have been keen to enter for some time."
Expobank's chairman Kirill Yakubovskiy will remain on the board at the bank and said the deal would mark a new era for Russian banking.