It was separated from Corinth renamed the Metropolis of Argos and Nafplio in 1189, confirming an earlier de facto merger with Nauplion.

According to the article "Argos and Orthodoxy Through the Passage of the Ages", written by the Archimandrite Kallinikos D. Korobokis, the diocesan homilist (published in the periodical "Eyes on Argolis", Volume 10, May–June 2002), the history of the metropolitan see is recorded as follows: Paulinus (354-431 AD) relates that the Apostle Andrew first proclaimed the Gospel at Argos, and thus he is traditionally held to be the founder of the Church there.

Argos acclaimed a bishop fairly early on, separate from that of the bishopric of Nauplia (Nafplio), with both under the jurisdiction of the Metropolis of Corinth.

Throughout the minutes of the Council of 879 in Constantinople, written by the members, the Bishop of Argos is recorded as Theotimos, and that of Nauplion as Andreas, which establishes a terminus post quem, but not a precise date for the unification.

Their names are as follows: In 1212, the local Orthodox hierarchy was replaced by Latin hierarchs during the period of Frankish rule in which the two towns formed part of the Lordship of Argos and Nauplia.

The bishop, Grigorios Kalamaras was killed in the Siege of Tripolitsa, and is consequently termed an ethnomartyr a national martyr, Greek: ἐθνομάρτυρας.

This designation is a popular one, and has no canonical status making the bishop a saint, as death in battle does not necessarily qualify one for martyrdom.

[2] According to the French theologian and scholar Michel Le Quien, these are the earliest bishops of Argos, as recorded in Greek and Latin sources:[3] Total monastics, 121.