During the Russian Revolution in 1917, Seljamaa participated as a delegate to the First All-Russian Congress of Soviets of Workers' and Soldiers' Deputies, and served as a member of the first All-Russian Central Executive Committee for the Estonian Labour Party.

[1] After graduating, Seljamaa returned to Estonia shortly after the country's declaration of independence in February 1918.

Together with Johan Laidoner he became Estonia's representative to the Soviet Union, and participated in the negotiations of the Treaty of Tartu in 1919 and 1920.

[2] In 1920, Seljamaa was elected to the I Riigikogu, but resigned in 1922 upon being appointed Estonian envoy in Latvia, a post he held until 1928; between 1925 and 1926 he was also accredited to Lithuania.

Seljamaa died in Tallinn, shortly after being appointed Estonian envoy in Rome.