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Coinfections affecting the porcine respiratory system have often been overlooked in favor of mono-infections, despite being much more common in the field. The term “porcine respiratory disease complex” (PRDC) is used to describe coinfections involving both viruses—such as the swine influenza A virus (swIAV), the porcine respiratory and reproductive syndrome virus (PRRSV), and the porcine circovirus type 2 (PCV2), as well as bacteria. Until recently, most studies were primarily focused on clinical aspects and paid little attention to the molecular consequences of coinfections. This narrative review addresses the consequences of coinfections in the porcine respiratory system involving viruses. Where possible, interactions between viruses are briefly discussed. Conversely, research involving bacteria, protozoa, and fungi has not been considered. Finally, the main limitations complicating the interpretation of results from coinfection/superinfection studies are outlined, along with future research prospects in this exciting field of health research.