His book Da'aa'im Al-Islam is full of narrations which are from the twelve Imams although he did not mention the names of the six Imams after Jafar Al-Sadiq (AS) due to the Fatimi rulers, but used a Kunyah like Abu Jafar for Imam Al-Jawad, Abul Hasan for Imam Musa Al-Kadhim, and Imam Ali Al-Hadi or a famous title like Al-'Aalim, Al-Saamir , Al-Taahir etc of those six Imams. If you go through the books of Qadhi Al-No'man , you will find plenty of points which are not accepted by the twelver Shia. Great Ulama like Al-Majlisi of Biharul Anwar, Bahrul Oloom, Al-Noori of Mustadrak Al-Wasaa'il and Sayyed Al-Khoo'ee who studies the books of Qadhi Al-No'man Al Masri confirmed that he is a follower of the Twelve Imams.

Wassalam.