Investigating the narrators’ reliability plays an important role in using traditions in inferring religious knowledge. Aḥmad b. Ḥilāl is one of the narrators who can be evaluated in various point of views: weakness, absolute trustworthiness, conditional trustworthiness, and illegitimacy. He has narrated about ninety traditions in jurisprudential, historical and religious matters, especially the issue of Mahdism, and this makes it necessary to investigate his position. The research is based on descriptive-analytical sources and evaluates his narrations' validity. In order to reach a solid conclusion about him, in the first step, his biography and his position in narrating traditions have been researched. In the last step, the weaknesses related to him in the three categories of cursing from the sacred persons, exaggeration, and the expression of denier tradition about him were examined and the criticisms related to each were explained. In the next step, his specific and general validation are explained using the following components: Being among the Tafsir-e Qomi and Al-Mazar al-Kabir narrators, and also religious elders’ narration from him. The research achievement has been organized based on the criticism of his weaknesses and the set of his general validities.