Porcine reproductive and respiratory syndrome (PRRS) has devastated the pig industry worldwide for almost 25 years, and its virus (PRRSV) preferentially infects and replicates in pulmonary alveolar macrophages (PAMs). To discover cellular protein responses in PRRSV-infected PAMs, two-dimensional liquid chromatography-tandem mass spectrometry coupled with isobaric tags for relative and absolute quantification (iTRAQ) labeling was employed to quantitatively identify the differentially expressed proteins between the PRRSV-infected groups and the controls. A total of 160 cellular proteins in PAMs that were significantly altered post-infection were identified. These differentially expressed proteins are related to the biological processes of virus binding, cell structure, signal transduction, cell adhesion, etc., and their interactions. This is the first report that analyzed the cellular protein profile of PRRSV-infected PAMs using iTRAQ technology, and this data provides important information to help understand the host response to PRRSV and to define the cellular requirements for the underlying mechanism of PRRSV replication and pathogenesis.