Thiersch in 1845 entered in the Academy of Fine Arts in Munich for studying painting, but he was also interested at the studying of sculpture. He was trained by Schnorr von Carolsfeld and then by Karl Schorn.
In 1847, Thiersch with his friend Piloty, went to Venice. He was in Rome from 1849 to 1852 and went to live on the second floor of a house in Piazza Barberini. With Oswald Achenbach, Heinrich Dreber and Albert Flamm he make several excursions into the Roman campagna.
After a trip to Sicily, went to Athens where he decorated the Byzantine church of St. Nicodemus and became a professor of art at the Academy of Fine Arts. Later he moved to Vienna (1860-1864), St. Petersburg (1864), London (1880) and Paris (1892).