Twenty-two of the 105 women who ran in Sunday's House of Councilors election won seats, up five from the previous Upper House election in 2010.
Eleven women were elected from both prefectural constituencies and via the proportional representation system.
While all nine women from the Liberal Democratic Party won, the overall percentage of women legislators remains low, at 18.2 percent. Their average age was 50.6.
The Democratic Party of Japan saw only four of its 10 female candidates elected.
Two women from the LDP's smaller partner, New Komeito, won, as did two from Your Party, three from the Japanese Communist Party, one from Nippon Ishin no Kai (Japan Restoration Party) and one other.
It is not clear how many women in total were fielded by each of the smaller parties, according to the Kyodo News report.