Before coming to Duke, Janiak earned an M.A. from Michigan while enrolled in its doctoral program, and a Ph.D. from Indiana in 2001, with a Ph.D. minor in history and philosophy of science. He wrote his dissertation under Michael Friedman, Fred Beiser, Paul Franks and Nico Bertoloni Meli.

In 2001-02, Janiak was a postdoctoral fellow at the Dibner Institute for the History of Science and Technology at MIT, having previously been a doctoral fellow at Tel Aviv University. He joined the Duke faculty in the fall of 2002.

In 2008-09, he received the Richard Lublin Distinguished Teaching Award from Duke's School of Arts and Sciences.