Abstract: Based on three-dimensional temperature and salinity data from 1961 to 2012, this study investigates the effects of the Indian Ocean Dipole (IOD) on the barrier layer thickness (BLT) in eastern tropical Indian Ocean during different phases of the Pacific Decadal Oscillation (PDO). The results show that during the warm PDO phase, the BLT decreases significantly in eastern equatorial Indian Ocean in positive IOD (pIOD) events, while the thickness changes little in negative IOD (nIOD) events. It is worth to note that the BLT decreases in pIOD events but increases in nIOD events during the cold phase of PDO. It reveals that the pIOD-induced easterly wind anomaly and thinning of isothermal layer are similar during different phases of PDO. However, the pIOD-induced positive precipitation anomalies in the cold phase of PDO are more significant than those in the warn phase, resulting in a decrease in surface salinity, shallower mixed layer, and negative BLT anomaly in eastern equatorial Indian Ocean. Consequently, the pIOD-induced negative BLT anomalies in the warm PDO phase are slightly larger than that in the cold PDO phase. Meanwhile, the nIOD-induced westerly wind anomalies in the cold phase of PDO are stronger than those in the warm phase, leading to stronger downwelling Kelvin waves and deeper isothermal layer and causing a more significant positive BLT anomaly in eastern equatorial Indian Ocean in nIOD events during the cold phase of PDO.