We derive an expression for the wave action flux of finite amplitude Alfv¿n waves in a multi-ion plasma. The expression is valid in the presence of dissipative forces and allows an arbitrary angle between the average mangetic field and the wave vector. Aplying the conservation of wave action and the first law of thermodynamics yields the following results for a multi-ion plasma: (1) an expression for the spatial evolution of Alfv¿n wave amplitude in the absence of dissipation. (2) the relationship between the wave amplitude and the dissipative heating, and (3) an expression for the acceleration of an ion species by finite amplitude Alfv¿n waves. The acceleration consists of two terms: a nondissipative wave pressure that is identical to that derived previously under more restrictive conditions, and a new term giving the acceleration that must accompany dissipative heating. These results are discussed in the context of the observations of heavy ions in the solar wind.