This paper investigates a problem of control of rotary slosh using integral sliding modes (ISM). Slosh coupled with vehicle dynamics represents a class of systems having coupled nonlinear and underactuated dynamics. Rotary slosh is modeled using spherical pendulum. The coordinates are chosen to avoid the singularity at equilibrium point. A stabilizing control is designed using Lyapunov approach. A stabilizing controller (SC) is made robust by adding ISM component. The integral sliding mode control (ISMC) yields robust performance over the entire state space. The effectiveness of the method is validated in simulations. © 2012 IEEE.