The two mortar shells are retrieved from the Bau Giang River in Quang Ngai Province on August 27.
Police in Tu Nghia Commune said the fisherman found the shells at around 12.30 pm and brought them ashore before reporting to local authorities.
Military command and police forces cordoned off the site and identified the shells as 60mm mortars left from the American War, still containing intact fuses.
The mortars were safely removed for controlled detonation.
Officials warned residents not to touch or move any suspected explosives but to notify police or military units immediately for safe handling.