This paper analyzes the problem of transmitting a Gaussian source over an additive white Gaussian noise (AWGN) channel in the presence of an unknown interference. The goal is to estimate the source at the receiver with minimum mean squared error (MMSE) distortion. We introduce a lattice-based coding scheme and calculate its achievable distortion. If the interference distribution and the lattice voronoi region satisfy some conditions, the effect of interference can be reduced.