Attested in the sources between 1360 and 1366. He appears as κῦρ, δοῦλος and οἰκεῖος of the Serbian Empress Jelena (Helene), δοῦλος of of the Serbian Despot Ioan Uglješa (Ioannes Unklesis) in the sources. He held the office of governor of Serres 1360. He repeatedly judged in a court as καθολικὸς κριτής between 1365 – 1366 in Serres. He was a member of ecclesiastical court, which was summoned by Iakobos, the Metropolitan of Serres (ἐξελέγημεν ἡμεῖς οἵ τε οἰκεῖοι τῇ κραταιᾷ καὶ ἁγίᾳ ἠμῶν κυρίᾳ καὶ δεσποίνῃ, ὅ τε μέγας παππίας Δούκας ὁ Νεστόγγος, Κομνηνὸς ὁ Εὐδαιμονοϊωάννης). He signed also the document issued by Iakobos in November 1360 concerning the metochion Saint Nicholas in Kamenikaia (ὁ δοῦλος τῆς κραταιᾶς καὶ ἁγίας ἠμῶν κυρίας καὶ δεσποίνης κεφαλὴ Σερρῶν Κομνηνὸς ὁ Εὐδαιμονοϊωάννης). He participated in the decision over a plot of land in the village Zetinon (Zintzu) and a Church of Saint George (τῶν εὐγενεστάτων καὶ καθολικῶν κριτῶν, ... κῦρ Δημητρίου Κομνενοῦ τοῦ Εὐδαιμονοϊωάννου). He with other members of the court ruled in favor of the Esphigmenu Monastery against the Kastamonitu Monastery. He signed the decision document issued by Sabas, the Metropolitan of Serres, in August 1365 (Ὁ δοῦλος τῆς κραταιᾶς καὶ ἁγίας ἡμῶν κυρίας καὶ δεσποίνης καθολικός κριτὴς Δημήτριος Κομνηνός ὁ ΕΥΔΑΙΜΟΝΟΙΩΑΝΝΗΣ). He attended the trial between Hilandar Monastery and Georgios Isaris (τοὺς καθολικοὺς κριτάς, τὸν ἐπὶ τοῦ κάστρου κῦριν Ὀρέστην καὶ τὸν κυρὸν Δημήτριον Κομνηνὸν τὸν Εὐδαιμονοϊωάννην). He together with other members of the court ruled in favor of the Hilandar Monastery and signed the charter issued on this occasion (ὁ δοῦλος τοῦ ἁγίου μου αὐθέντου τοῦ πανευτυχεστάτου δεσπότου, Δημήτριος Κομνηνὸς ὀ Εὐδαιμονοϊωάννης).