Paule Kuzmickiene, a member of Vilnius' City Council, won 52.03 percent of the vote in the capital's Zirmunai constituency and Rasa Petrauskiene, the other conservative, received 50.53 percent in Gargzdai, in western Lithuania.
Social Democrat Liudas Jonaitis garnered around 54 percent of the vote in the Ziemgala constituency covering the northern districts of Pakruojis and Joniskis and part of Siauliai District.
This brings the number of Homeland Union MPs in the Seimas to thirty-six. The LSDP will now have nine seats in the parliament.
The by-election was held just over a year before the next general election scheduled for October 2020.
The newly-elected MPs will take office after being sworn in in the parliament.