Arsenios 4 was a Stoudite monk; he wrote to Theodoros 15 (Theodore the Stoudite) in 809 and received a letter in reply, in which Theodoros 15 condemned the Moechian synod and added that Arsenios 4 would hear a description of it from Euprepianos 1; Arsenios 4 is addressed as τέκνον ποθεινότατον: Theod. Stud., Ep. 38 (a. 809; addressed Ἀρσενίῳ τέκνῳ).

Arsenios 4 was one of the Stoudite monks whom Theodoros 15 proposed to identify by use of a code letter, for security reasons, in 809/811: Theod. Stud., Ep. 41 (one of the ἀδελφοί). He was one of those who, like Naukratios 1 and Ioannes 460 refused to talk to Leontios 29: Theod. Stud., Ep. 43 (in 809/811). Arsenios 4 suffered persecution, imprisonment and exile for opposing the Moechian synod: Theod. Stud., Ep. 48 (a. 810/811). By 815/817 he was dead (τῷ ἀειμνήστῳ Ἀρσενίῳ); he was once served by Kallistos 14: Theod. Stud., Ep. 216.

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