The article covers the influence of Pope Francis’ Apostolic Letter motu proprio Mitis Iudex Dominus Iesus on the scope of the principle of contradiction in matrimonial nullity trials. This article will present certain remarks concerning the effect of Pope Francis’s process reform on the extent of the principle of contradiction in respect of such constituting factors of that principle as: the libellus; identification of the subject-matter of the process. In conclusion, it should be stated that Pope Francis’ trial reform of 2015 extended the scope of the principle of adversarial in matrimonial nullity trial.