Shazar was born in Russia to a family of Habad Hasidim, but at an early age, he left the path of Hasidism for that of Zionism. He always retained a strong emotional attachment to Hasidism and in his later years established close, personal contact with the Lubavich (Habad) Rebbe of New York.

Shazar began his Zionist activities while still in his teens, and by the age of 18 had already served a two-month jail sentence in Russia for his activities in the Po'alei Zion movement. On his release he took up the study of Jewish history, and at the same time began a long career as an editor and writer for Yiddish newspapers in Russia and the United States. His interest in Jewish history brought him to Germany in 1912 to pursue university studies. He eventually developed into a scholar and writer on East European Jewish history, the Shabbatean movement, and Bible criticism.

Shazar the student and scholar did not, however, forego his Zionist activities while in Germany, and remained active in the Po'alei Zion movement. He settled permanently in Palestine in 1924 and combined his Zionism and writing talents in his position as editor of the Histadrut daily newspaper, Davar, and later as editor-in-chief of the Histadrut publishing house, Am Oved. He also wrote poetry, essays, autobiographical fiction, biographies and scholarly articles.

In recognition of his vast intellectual achievements and extensive Zionist activities, the Israel government appointed Shazar the first minister of education and culture in 1949, and in 1963 the Knesset elected him president of the State of Israel, a position he held until his retirement in 1973.