In 2000, he supported a law passed on 13 June by the Seimas seeking compensation from Russia for damages inflicted during the illegal Soviet occupation of Lithuania and the Baltics, a key issue for the prime minister and Homeland Union.

[3] Kubilius led the Homeland Union – Lithuanian Christian Democrats Party into elections on 28 October 2008.

His Homeland Union won the election representing a victory for Lithuania's center right after seven years of leftist rule.

[9][10] He was active in seeking financial compensation from Russia for the illegal Soviet occupation of Lithuania, labeling the issue a priority upon taking office in 2008.

[16] Among his accomplishments were reining in public expenditures, preparation to join the Eurozone, and reform of the energy sector.

[17] According to The Economist, "the election came too early for Mr. Kubilius to benefit from a recovery from the painful austerity measures that he imposed when he realised that Lithuania risked becoming the Baltic Greece.

[20] In November 2021, Kubilius joined a group of seven Members of the European Parliament led by Raphaël Glucksmann to Taiwan to send a strong signal in support of the self-ruling island, despite a threat of retaliation from China.

[23] Accepting the role, Kubilius stated, "My critical view of the Kremlin regime was formed long ago, and it is unchanging.

[24] He praised Turkey for "proving thrice [in Syria, Libya and Nagorno-Karabakh] that the Kremlin fears the fist.

[26] He led the call by the European People's Party for sanctions against all those responsible for Russia's poisoning of Alexei Navalny.

[29] In September, President von der Leyen allocated the Defence and Space portfolio to Kubilius.