We investigate the link between birth order and the career outcome of becoming Chief Executive Officer (CEO) of a company. CEOs are more likely to be the first-born, i.e., oldest, child of their family relative to what one would expect if birth order did not matter for career outcomes. Both male and female CEOs are more likely to be first-born. However, the first-born advantage seems to largely reflect the absence of an older brother, but not of an older sister. These results are more pronounced for family firms, where traditionally the oldest child is appointed to run the family business, but also hold for non-family firms.