"Celestina" scholarship has devoted many pages to the influence of "Cárcel de amor" on the "Tragicomedia de Calisto y Melibea". However, this is not the only work by Diego de San Pedro that has left trace in the "Tragicomedia". Actually, his religious writings "La Passion trobada" and "Las siete Angustias de Nuestra Señora" could have played an important role in the composition of the tragic ending of "Celestina". In this article, I will enumerate the arguments in favour of the influence of the religious writings of Diego de San Pedro on "Celestina", both textual and structural. Moreover, I will offer a brief explanation on why and how San Pedro's religious poems were chosen to build the final acts of "Celestina".