Sr2TiCrO6 ceramic samples were prepared via solid-state method, and their dielectric properties were systematically investigated. Colossal dielectric behavior was found to occur near room temperature, and two dielectric anomalies were observed around 620 and 820K. The colossal dielectric behavior follows the dual-relaxation mechanism, which is composed of a dipolar relaxation associated with the defect dipole pairs of OHO-Cr3+ and a Maxwell-Wagner relaxation due to the surface-layer effect originated from humidity sensitivity. The low-temperature anomaly is considered to be a pseudo-relaxor behavior caused by oxygen vacancies, and the high-temperature anomaly results from negative capacitance due to the carriers changing from localized state to free state.