Leal was elected a member of the National Academy of Engineering in 1987 for fundamental contributions to the understanding of the fluid mechanics of particulate systems, polymer solutions, and suspensions.
Leal started his academic career in 1970 as an assistant professor in chemical engineering at California Institute of Technology. He became full professor in 1978. During 1986–1989, he was Chevron Distinguished Professor of Chemical Engineering. In 1989, Leal joined University of California, Santa Barbara as Professor and Chair in the Department of Chemical Engineering. He is currently the Warren and Katharine Schlinger Professor of Chemical Engineering at UCSB.
Leal's research covers a wide range of topics in fluid dynamics, including the dynamics of complex fluids, such as polymeric liquids, emulsions, polymer blends, and liquid crystalline polymers. He also works on large-scale computer simulation of complex fluid flows. Leal and his coworkers made pioneering contributions to the study of drop deformation under different flow conditions. They have developed a scheme based on a finite difference approximation of the equations of motion, applied on a boundary-fitted orthogonal curvilinear coordinate system, inside and outside the drop. Leal has published more than 250 papers on fluid dynamics. He has directed 55 Ph.D. thesis in various topics in fluid dynamics. Several of his students have gone on to become professors at prestigious universities including Howard Stone who is currently at Princeton and Gerald Fuller at Stanford. Leal comes from a long line of researchers that can be traced back from mentor to mentor all the way to Sir Isaac Newton. 
^ ab"Array of Contemporary American Physicists | L. Gary Leal". American Institute of Physics. Archived from the original on 4 October 2012. Retrieved 11 September 2010.
^Ryskin, G.; L. G. Leal (1984). "Numerical Solution of Free-Boundary Problems in Fluid Mechanics. Part 1. The Finite-Difference Technique" (PDF). J. Fluid Mech. 148: 1–17. Bibcode:1984JFM...148....1R. doi:10.1017/S0022112084002214.
^Kang, I. S.; L. G. Leal (1987). "Numerical Solution of Axisymmetric Unsteady Free-Boundary Problems at Finite Reynolds Number. I. Finite difference Scheme and its Application to the Deformation of a Bubble in a Uniaxial Straining Flow". Phys. Fluids. 30 (7): 1929–1940. Bibcode:1987PhFl...30.1929K. doi:10.1063/1.866207.
^"Neurotree -- Connection from L. Gary Leal to Isaac Newton". Retrieved 6 March 2020.
^Kim, John; Leal, L. Gary (2008), "Editorial: Fifty years of Physics of Fluids", Physics of Fluids, 20 (1): 010401–010401–5, Bibcode:2008PhFl...20a0401K, doi:10.1063/1.2832366, S2CID 122376358