His major research interests[1] are neutrino physics, unification of elementary particle forces, baryon and lepton number violation and supersymmetry.

Senjanović is best known for the seesaw mechanism, which he proposed together with Rabindra Mohapatra in 1979,[2] independently of Peter Minkowski, Sheldon Glashow, Murray Gell-Mann, Pierre Ramond, Richard Slansky and Tsutomu Yanagida.

In the works of Minkowski, and Mohapatra and Senjanović, the smallness of neutrino mass is related to the maximality of parity violation in weak interactions.

Senjanović, together with Mohapatra, Jogesh Pati and Abdus Salam, is one of the proponents of the left-right symmetric theory of electroweak interactions,[3] introduced in order to understand the origin of parity violation in nature.

Following the original suggestions of Savas Dimopoulos, Stuart Raby and Frank Wilczek, and Luis Ibáñez and Graham G. Ross, together with William J. Marciano, he showed[6] in 1981 that the supersymmetric unification was tied to the large top quark mass, around 200 GeV, years before experiment.