Alan Hájek studied statistics and mathematics at the University of Melbourne (B.Sc. (Hons). 1982), where he won the Dwight Prize in Statistics. He took an M.A. in philosophy at the University of Western Ontario (1986) and a Ph.D. in philosophy at Princeton University (1993), winning the Porter Ogden Jacobus fellowship. He has taught at the University of Melbourne (1990) and at Caltech (1992-2004), where he received the Associated Students of California Institute of Technology Teaching Award (2004). He has also spent time as a visiting professor at MIT (1995), Auckland University (2000), and Singapore Management University (2005). He joined the Philosophy Program at RSSS, ANU, as Professor of Philosophy in 2005.

He has been a Fellow of the Australian Academy of the Humanities since 2007. He was the President of the Australasian Association of Philosophy, 2009-10. He won the American Philosophical Association Article Prize for “the best article published in the previous two years” by a “younger scholar”, for “What Conditional Probability Could Not Be”, 2004. Two of his articles were selected by The Philosopher’s Annual as “one of the ten best articles in philosophy” in the previous year: “Waging War on Pascal’s Wager” (2004), and “Degrees of Commensurability and the Repugnant Conclusion”, with Wlodek Rabinowicz (2022). He received the ANU College of Arts and Social Sciences Award for Excellence in Supervision (2012), and the university-wide Vice Chancellor’s Award for Excellence in Supervision (2013).

Hájek's research interests include the philosophical foundations of probability and decision theory, epistemology, the philosophy of science, metaphysics, and the philosophy of religion. His paper "What Conditional Probability Could Not Be" won the 2004 American Philosophical Association Article Prize for "the best article published in the previous two years" by a "younger scholar". Two of his articles were selected by The Philosopher’s Annual as “one of the ten best articles in philosophy” in the previous year: “Waging War on Pascal’s Wager” (2004), and “Degrees of Commensurability and the Repugnant Conclusion”, with Wlodek Rabinowicz (2022).