A theoretical analysis is presented to solve the problem of foundation isolation from vibrations generated in the neighborhood using piles as barriers. The problem is formulated in two and three dimensions as one of multiple diffractions of elastic waves. The solution is determined imposing continuity and equilibrium conditions at the soil‐pile interfaces with the aid of Graf's addition theorem. For the two‐dimensional model the exact solution is obtained. The diffracted field by each pile is constructed as expansions of cylindrical wave functions. For the three‐dimensional model an approximate solution is obtained. In this approximate solution the diffracted field by each pile is constructed only with Rayleigh waves. A parametric analysis is done to study the influence of the diameter of the piles, the separation between them, and their length on the effectiveness of the barrier. A transmissibility index is defined to measure the effectiveness of this isolation system.