According to sociological agency Gallup Korea, Moon's actions are now approved by just 43 percent of South Koreans, while 46 percent of respondents disapprove of them. The rating of the South Korean leader fell for the fourth consecutive week, the pollster noted.
The poll was conducted from Tuesday to Thursday among about 1,000 people.
The second meeting between US President Donald Trump and North Korean leader Kim Jong-un took place in Hanoi on 27-28 February. Many experts expected a joint declaration on the results of the talks, but the negotiations on denuclearisation of the Korean Peninsula between Trump and Kim ended with no documents signed.
The summit fell apart after North Korea requested Washington to lift all sanctions on the country before it started denuclearising, to which the United States could not agree.