Adamic was born at the Praproče castle in Blato near Grosuplje, in what is now Slovenia (then part of the Austro-Hungarian Empire). The oldest son of a peasant family, he was given a limited childhood education at the city school and, in 1909, entered the primary school at Ljubljana.
Early in his third year he joined a secret students' political club associated with the Yugoslav Nationalistic Movement that had recently sprung up in the South-Slavic provinces of Austria-Hungary. Swept up in a bloody demonstration in November 1913, Adamic was briefly jailed, expelled from school, and barred from any government educational institution. He was admitted to the Jesuit school in Ljubljana, but was unable to bring himself to go. "No more school for me. I was going to America," Adamic wrote. "I did not know how, but I knew that I would go."
On December 31, 1913, at the age of 14, Adamic emigrated to the United States.[2] He finally settled in the Croatian fishing community of San Pedro, California. He became a naturalized United States citizen in 1918. At first he worked as a manual labourer and later at a Slovenian daily newspaper, Narodni Glas ("The Voice of the Nation"), that was published in New York. As an American soldier he participated in combat on the Western front during the First World War. After the war he worked as a journalist and professional writer.
All of Adamic's writings are based on his labour experiences in America and his former life in Slovenia. He achieved national acclaim in America in 1934 with his book The Native's Return, which was a best seller directed against King Alexander's regime in the Kingdom of Yugoslavia. This book gave many Americans their first real knowledge of the Balkans. It contained many insights, but proved far from infallible: Adamic predicted that America would prosper by eventually "going left", i.e. turning socialist.