We report squeezed polariton generation using parametric polariton four-wave mixing in semiconductor microcavities in thestrong coupling regime. The geometry of the experiment corresponds to degenerate four-wave mixing, which gives rise to abistability threshold. Spatial effects in the nonlinear regime are evidenced, and spatial filtering is required in orderto optimize the measured squeezing. By measuring the noise of the outgoing light, we infer a 9 percent squeezing on thepolariton field close to the bistability turning point.