The addition of a certain amount of trans-1,4-polyisoprene (TPI) to the rubber compounds for tire tread can significantly reduce the rolling resistance and heat buildup of the tire. Because TPI is a crystalline polymer, controlling the crystallinity and crystal size of TPI might lead to the improvement in the mechanical properties of TPI blends with other rubbers, thus improving the tire performance. In this article, the effects of processing temperature and bis-(γ-triethoxysilylpropyl)-tetrasulfide (Si69) on the crystallization and mechanical properties of solution-polymerized styrene-butadiene rubber (SSBR)/TPI vulcanizates were studied. The addition of Si69 to SSBR/TPI or increasing the processing temperature could significantly decrease the melting point and crystallinity of TPI as evidenced by differential scanning calorimetry analysis, and smaller-size and less-perfect crystals of TPI appeared as observed by polarized optical microscopy. With increasing processing temperature, the tensile strength of the SSBR/TPI vulcanizates decreased while the elongation at break increased. After the addition of Si69, the tensile strength increased while the elongation at break decreased. The glass transition temperature of SSBR in SSBR/TPI vulcanizates was affected by changing the processing temperature. The processing temperature and the addition of Si69 can significantly affect the structure and properties of SSBR/TPI vulcanizates. Keywords: trans-1, 4-polyisoprene, solution-polymerized styrene-butadiene rubber, crystallization, properties, vulcanizate