Born into a large family in the village of Bailovo near Sofia, he loved writing and reading from an early age. Studying to become a teacher, he taught for a year in 1895 in his native village. He was first published in 1901, and the respect it earned him in literary circles encouraged him to go to Sofia in 1903, where he worked as a librarian at the university library. It was during this period he took his now-famous pseudonym from the word pelin, which means wormwood in Bulgarian. He spent 1906-07 in France, perfecting his skills in the language. By this time, he was already a popular writer.

Between 1910 and 1916, he was the director of special collections at the National Library and also served as editor of numerous magazines, including the children’s publication Veselushka. Additionally, he served as a war correspondent during World War I.

In 1911, one of his most famous works appeared, The Gerak Family (Bulgarian: Geratsite). It is one of the best-known pieces of Bulgarian literature and deals with a traditional village family experiencing the transition from the simplicity of rurality to the modernization of Bulgarian society, a world in which old time practices founded on family love and dedication to the land start to disappear. His second great work, Earth (Bulgarian: Zemya), was published in 1922. In this book, Pelin created a gallery of characters who identified with the national character and conscience.

From 1924 until 1944, Pelin served as conservator at the Ivan Vazov Museum, all the while continuing to write, mostly for children, and be published. In 1940, he was named president of the Union of Bulgarian Writers.