The Vietnam Football Federation (VFF) said top officials unanimously agreed to dispense with Miura, 52, who had not achieved the results they wanted from both the national and under-23 teams he coached.
"Through discussion and analysis, the meeting agreed with an assessment that tactics of the national team and the under-23 national team need to be suitable with the size and physical condition of Vietnamese players," the VFF said in a statement.
"Coach Toshiya Miura, though he tried very hard, has been unsuccessful."
Miura's early exit comes after what local media said were complaints by domestic clubs about players getting injured or exhausted while on national team duty.
Miura was in charge of Vietnam when they were thumped 8-1 by Premier League giants Manchester City in Hanoi on their pre-season tour in July.
Vietnam are currently third in Group F of the second round of Asian qualifying for the 2018 World Cup in Russia, trailing Thailand and Iraq and looking out of contention.
The national side are 146th in FIFA's rankings and their most memorable achievement was winning the 2008 Suzuki Cup, the Southeast Asian championship.
(Reporting by Mai Nguyen and Martin Petty, editing by Alan Baldwin)
