An object of the present invention is to provide a conjugated diene polymer composition which can be prepared into a rubber compound product (such as a tire tread) ensuring a good balance between fuel efficiency and wet grip performance, and having high breaking properties, a small change in breaking strength after heating, and a small change in breaking properties for a prolonged vulcanization time, when vulcanized; and the conjugated diene polymer composition having a high compounding freedom which enables adjustment of the glass transition temperature.
The conjugated diene polymer composition comprises conjugated diene polymers (A) and (B) each having a specific amount of aromatic vinyl monomer units and a specific iodine value, wherein (SP value of (A) - SP value of (B)) is 0 MPa 1/2 or more and 0.8 MPa 1/2 or less, |iodine value of (A) - iodine value of (B)| is 100 I g/100 g or less, and |glass transition temperature of (A) - glass transition temperature of (B)| is 10°C or more and 60°C or less.