In 1989 he obtained his doctoral degree at the Heidelberg University in Germany with a thesis in celestial mechanics written under the direction of Willi Jäger.
[2] After a visiting position at the University of Dortmund, Diacu immigrated to Canada, where he became a post-doctoral fellow at Centre de Recherches Mathématiques (CRM) in Montreal.
Since 1991, he was a professor at the University of Victoria in British Columbia, where he was the director of the Pacific Institute for the Mathematical Sciences (PIMS) between 1999 and 2003.
Diacu also obtained some important results on a conjecture due to Donald G. Saari,[6][7] which states that every solution of the n-body problem with constant moment of inertia is a relative equilibrium.
In 2015 Diacu was presented with the J. D. Crawford Prize from SIAM, awarded for outstanding research in nonlinear science,[10] "for the novel approach to the n-body problem in curved space, blending dynamical systems, differential geometry, and geometric and celestial mechanics in a lucid, inspirational manner.