The spin-statistics theorem is a cornerstone of physics, linking particle spin to its fermionic or bosonic nature in unitary quantum field theory. This talk presents a novel proof of this theorem within the framework of unitary TQFTs using so-called dagger categories. Our method draws upon the perspective on dagger categories by anti-involutions and Hermitian forms, which I jointly developed with Jan Steinebrunner. This approach not only provides a clearer understanding of the spin-statistics theorem, but also offers valuable insights into symmetric monoidal dagger categories.