Biomechanics is concerned with the behavior of living tissues when subjected to the action of forces, and the subsequent effects of these living tissues on their environment. In terms of the pulmonary vasculature, we can consider the vascular tissue and the blood as “physical bodies,” and concern ourselves with the biosolid and biofluid mechanics principles, respectively, that govern their behavior. In the cardiovascular system, it is generally the blood flowing through the vasculature that exerts forces (e.g., pressure and shear) on the vascular tissue. When the arterial tissue responds to these forces, it subsequently affects the rate and pattern of blood flowing through it, which is its “environment.” Indeed, the interactions between blood flow and the vascular walls are so interrelated that an entire branch of biomechanics is devoted to them – the area of biofluid–biosolid interactions. The mechanics of the pulmonary vasculature are particularly complex because blood flow can be affected not only by the vascular tissue (and vice versa) but also by the state of the airways, especially in the lung capillaries. We begin this chapter by considering the mechanical behavior of blood vessels independent of airways and introduce some basic concepts important to biomechanics, such as stress and strain. We also briefly review some key concepts in biofluid mechanics (e.g., resistance, Reynolds number, and Womersely number) and the mechanical behavior of blood vessel constituents. The subsequent sections are focused on the mechanics of the pulmonary vasculature specifically. First, a review of the mechanics of large pulmonary arteries is presented followed by comments on the intermediate and small vessels in the intra-alveolar region. Next, the effects of breathing on pulmonary vascular mechanics are addressed and the effects of pulmonary vascular tissue mechanics on pulmonary vascular blood flow dynamics are discussed. Finally, we consider the impact of some disease states on these aspects of pulmonary vascular mechanics and conclude with a summary.