His birthplace was Hegybánya, then in the Kingdom of Hungary, now in Slovakia and now called Štiavnické Bane.
After attending school in Selmecbánya (now called Banská Štiavnica), Sándor Jávorka studied at the University of Budapest and graduated in 1906 with a thesis on the genus Onosma.
Since 1905 he was employed in the Department of Botany of the Hungarian National Museum, where he worked until 1940, latterly as its director.
The focus of Jávorka's scientific work was plant taxonomy and the Flora of Hungary, Bulgaria, Yugoslavia and Albania.
His main works include the Flora Hungarica (1924–25) and the complementary illustrated version Iconographia Florae Partis Austro-Orientalis Europae Centralis (1929 to 1934, with co-author Vera Csapody), besides several identification books and a biography of the Hungarian botanist Pál Kitaibel.