Results of the first theoretical study of the electronic structure of all the molecular states of BaLi dissociating into the six lowest limits Ba+Li are reported. The method used is similar to that used previously with success to describe the molecule BaH [J. Chem. Phys. 96, 7646 (1992)]. For the bound states (2,4)Lambda((+/-)) (spin-orbit effects neglected) and Omega((+/-)) (spin-orbit effects included), all previously unknown values of a set of spectroscopic constants are displayed. They have been very helpful in the analysis of the (2)(II)-I-2-->X(2) Sigma(+) system of BaLi recently observed in our laboratory and presented in the following paper. An agreement of approximate to 1.5% for the energy T-e of the (2)(II)-I-2 state, as well as for rotational constants B-v=0 of both states (2)(II)-I-2 and X(2) Sigma(+), and of approximate to 9% for the spin-orbit parameter A(v=0) of the (2)(II)-I-2 state, is obtained between theoretical predictions and experimental observations.