Cegelski studied chemistry at SUNY Binghamton in New York and graduated summa cum laude and a member of Phi Beta Kappa in 1998. She then worked in the lab of Jacob Schaefer at Washington University in St. Louis (WUSTL), earning a PhD in Biophysical Chemistry in 2004. Her post-doctoral work was in Molecular Microbiology at the Washington University School of Medicine.