On 10 May 2012, Pope Benedict XVI appointed him Metropolitan Archbishop of Seoul to succeed Cardinal Nicholas Cheong Jin-suk.

As a symbolic gesture, the ceremony was held on the 62nd anniversary of the outbreak of the Korean War, praying especially for the reconciliation and reunification of the two Koreas.

His ministry has also been marked by constant references to the precious faith of martyrs which is seen an example of authentic testimony all Christians should follow no matter what their life condition or state.

He also expressed a strong eagerness for dialogue, reconciliation and peace between the two Koreas to calm the tensions that are circling the peninsula, introducing the risk of a new conflict.

[7] As Archbishop of Seoul, Yeom heads the largest local Church in the Koreas and is also the apostolic administrator of Pyongyang, the North Korean capital.

By papal appointment, he participated in Third Extraordinary General Assembly of the Synod of Bishops from 5 to 19 October 2014 on the theme "The Pastoral Challenges of the Family in the Context of Evangelization".

[12] The coat of arms of Archbishop Yeom features the Traditional Red Hat, or the galero, replaces the Green one with its 15 tassels dangling in two five-tiered formations from either side.

Below the Red Hat is the Crucifix symbolizes the Holy Martyrs of Korea who were the victims of religious persecution against the Catholic Church during the Joseon dynasty in the 19th century.

An anchor cross and the two Greek letters "A" (Alpha) and "Ω" (Omega) that all the hopes and aspirations of the Korean People will be in the God's plan.

Yeom told reporters after his return from the one-day visit that seeing South and North Koreans working in harmony gave him hope that the two countries can "overcome their pain and sorrow."

The joint industrial park, located just north of the heavily armed border, is the last remaining cross-border rapprochement project between the rival Koreas.