Slavici was born in the village of ?iria, near Arad, in 1848, the Revolutionary year throughout Europe, with ramifications in Transylvania (then part of the Austrian Empire). Until 1868, Slavici studied at local Orthodox school and various other institutions in Transylvania, being taught in either Hungarian or German, as teaching in Romanian was strictly forbidden.

When he finished his studies, Slavici left Transylvania for Budapest, where he intended to study law. The following year, however, financial difficulties forced him to return home and take a job as a notary public. Throughout his employment, Ioan Slavici saved the money that would help him continue his studies.

In 1871, he left for Vienna as part of his military service. This proved to be a decisive moment in the life of the future writer, as Slavici had a chance to meet Mihai Eminescu, the most important Romanian poet, who was studying at the city University. The two became good friends, with Eminescu encouraging and assisting Slavici in the development of his style and of the works themselves. The same year marked Slavici's literary debut in Convorbiri Literare, the mouthpiece of the Junimea society in Ia?i.

In 1872, Slavici again had to interrupt his studies because of financial difficulties. Two years later, he left Austria-Hungary and moved to Ia?i, where he took part in the Junimea gatherings. In 1874 the Ioan Slavici Classical Theatre was established in his town of Arad. His first book, Nuvele din popor, a collection of short stories, was published in 1881. It included Moara cu noroc and Budulea Taichii, two of Slavici's most well-known and crafted works.

In 1882, he was selected as a corresponding member of the Romanian Academy. In 1884, Slavici moved back to Transylvania, becoming actively involved in the Romanian national movement, serving as a member of the Central Committee of the Romanian National Party, the main political forum of Romanians in the region. Hungarian authorities sentenced Slavici to one year in prison for his nationalist stance. This was the first of many short stays in prison in Slavici's life (not all of them connected with his political attitudes - some where the outcome of lawsuits against other journalists).

Six years later, he moved to Bucharest and, in 1894, he began publishing the first parts of his most famous novel, Mara, which was published as a single volume 12 years later. This is also the period of his activities as editor of Vatra magazine, alongside George Co?buc and Ion Luca Caragiale.

In 1909, Slavici began work for the pro-German newspaper Ziua. With the outbreak of World War I, his attitude brought him into conflict with other intellectuals who supported the Triple Entente powers. On August 14, 1916, Romania entered the War on the Entente side, and had most of its territory (including Bucharest) occupied by the German, Austro-Hungarian and Bulgarian troops in the summer of 1917.

The Romanian legitimate government took refuge in Ia?i, with the Central Powers establishing a puppet administration for the occupied lands. Slavici collaborated with the new government, being employed as editor of the official journal, the Bucharest Gazette. After the German withdrawal in November 1918, he was put on trial for his wartime activities and spent one year in jail, while his reputation with the intelligentsia was forever tarnished.

Slavici ended his life in Panciu (Vrancea county).

In contrast to the Junimea leadership (but consistent with the attitudes expressed by some of the group's members), Slavici was a noted antisemite. His early definition of Jews as "a disease" was doubled by his arguments in favor of their violent expulsion from Romanian soil:

"The solution that remains for us is, at a signal, to close the borders, to annihilate them, to throw them into the Danube right up to the very last of them, so that nothing remain of their seed!"

Later on, Slavici considered that:

"The hatred that has welled up against these people is natural, and this hatred can easily be unleashed against all of them that have inherited wealth or acquired it themselves, and could lead at the end to a horrible shedding of blood."