Vibrational predissociation of I2Xn (X=Ne, Ar) van der Waals clusters are studied in real-time using picosecond pump–probe (LIF) and molecular beam techniques. The state-to-state rates of vibrational predissociation are measured for specific vibrational levels v′i by monitoring the rise of nascent I2. Here, we report our study of I2X(B,v′i)k(v′i,v′f) →I2(B,v′f)+X. For I2Ne, the values of τ=k−1(vi,v′f) decrease nonlinearly from 216 ps for vi=13 to 53 ps for v′i=23. For I2Ar (B,vi), which undergo electronic and vibrational predissociation, the risetime of the nascent I2 is found to be 70 ps when v′i=18 and 77 ps when vi=21. A number of theoretical models for vibrational predissociation (the energy-gap law, the momentum-gap law, quantum and classical calculations) are compared with our experimental results in an attempt to understand the key features of the dynamics and the potential energy surface.