What does social cohesion require in culturally diverse post-immigration societies? Immigration and social cohesion are believed to be incompatible in the public debate. In normative political philosophy, a similar line of argument claims that social cohesion–based on a common national identity–is incompatible with immigration. In so doing, its proponents justify restrictive border policies. In this chapter, I will critically engage with this argument by reconnecting the literature in social sciences with normative political philosophy. I will offer a conditional and pro-tanto argument that social cohesion in post-immigration societies justifies open and non-discriminatory border policies. My argument is conditional in two senses, first because it assumes social cohesion is based on a common identity, and second because it only applies to the societies with significant cultural, religious, and ethnic diversity that can be best described as post-immigration societies. My argument implies that liberal nationalists have a choice: they can either keep defending social cohesion in the traditional way, which means that it will come with open borders or they can abandon this view, thereby losing one of the strongest justifications for restrictive borders.