HCN is an attractive biological precursor that is vital in creating proteins and the nucleobase adenine, and it is known to be created in planetary atmospheres. However, the formation pathways of HCN in both Titan’s and early Earth’s atmosphere has not been fully described. While previous studies have modeled the atmosphere of Titan, they exclude HCN2, which forms from CH + N2 and reacts with H to form HCN. Here, we extend a photochemical model for Titan’s atmosphere by adding HCN2 and reactions involving it. To constrain the rate coefficients of these reactions, we compare our results to Cassini data of Titan’s atmosphere and create a box model to simulate the laboratory setup of Trainer et al. (2012), which measured the nitrogen content of photochemical aerosols. Modern-day Titan has atmospheric chemistry similar to the chemistry in the Archean atmosphere. By determining the rate coefficients of the reactions of HCN2 that likely occur on Titan, we can further determine the amount of HCN2 and HCN in Earth’s early atmosphere. This information will provide a more robust understanding of the conditions that led to the spontaneous generation of life on Earth and that could form life elsewhere in the universe.