Neutrinos play multiple roles in Big Bang Nucleosynthesis (BBN).  Primarily, electron-flavor neutrinos interconvert neutrons and protons, thereby setting the neutron-to-proton ratio.  Precise calculations of the weak interaction rates require a detailed treatment of the out-of-equilibrium neutrino spectra and accurate values of weak constants.  I will discuss how the helium-4 and deuterium yields depend on the weak interactions and give an exposition on how we use the neutron lifetime to calculate the weak rates.  Furthermore, I will show the sensitivity of the primordial helium-4 yield to the underlying neutrino distributions and neutron lifetime.  I will conclude by discussing other isotopes present in BBN such as helium-3 and lithium.