Visa is required for citizens of Northern Ireland to visit Vietnam. Irish nationals may have 2 options: Visit Vietnam embassy in Northern Ireland or apply for a visa on arrival to Vietnam from Northern Ireland online. Irish citizens may apply for both tourist and business visa to Vietnam for the stay of 1 to 6 months from Northern Ireland. Please check this link for visa fee for Irish citizens.
All the information for getting a visa from Vietnam embassy in Northern Ireland can be found here: updating...