Baernstein matriculated at the University of Alabama, but after a year there he transferred to Cornell University, where he received his bachelor's degree in 1962. After working for a year for an insurance company, he became a graduate student in mathematics at the University of Wisconsin-Madison, where he received his master's degree in 1964 and Ph.D. in 1968.[2]
The main focus of Baernstein's was analysis, especially function theory and symmetrization problems. His most important contribution is now called the Baernstein star-function. He originally introduced the star-function to solve an extremal problem posed by Albert Edrei in Nevanlinna theory. Later, the star-function was applied by Baernstein and others to several different extremal problems.[3]
In 1978 he was an Invited Speaker with talk How the *-function solves extremal problems at the ICM in Helsinki.[4] He supervised 15 doctoral students,[5] including Juan J. Manfredi.
Baernstein, Albert (1986). "Coefficients of univalent functions with restricted maximum modulus". Complex Variables and Elliptic Equations. 5 (2–4): 225–236. doi:10.1080/17476938608814143.