Nearly two-thirds (64 per cent) of respondents to a poll conducted by the Kyodo News agency were in favour of marriage equality.
Roughly the same number (64.3 per cent) said new laws were needed to promote a better understanding of sexual diversity in Japan.
Just one quarter (24.9 per cent) were opposed to same-sex marriage.
The findings come just a few months after a Japanese court upheld a ban on same-sex marriage.
It did, however, rule that the lack of legal protection for same-sex families was violating their human rights.
READ MORE: Japan court upholds ban on same-sex marriage but urges for more LGBTQ+ protections
The survey was conducted just one week after Prime Minister Fumio Kishida fired an aide who made homophobic comments about not wanting to live next to LGBTQ+ couples and expressed a desire to leave Japan if same-sex marriage was introduced.
Almost six in 10 (57.7 per cent) of respondents believed the comments were inappropriate, according to the poll.
The overall approval rating for Kishida’s government stood at 33.6 per cent, a number roughly the same as in January.
A total of 424 households and 636 mobile phone users took part in the survey.