Spin-3/2 fields are the next spin multiplet we look for in the general particle search. Although these fields can be either fundamental vector-spinors or just excited leptons and quarks we assume that they are fundamental throughout this thesis. These higher-spin fields, described by the Rarita-Schwinger equations have to obey certain constraints to have correct degrees of freedom when they are on the physical shell. \par In the first chapter after the introduction, we introduce these spinor-vector fields to the reader by first going through the different representations that can be employed to describe them. We then recapitulate some facts on the most general free lagrangian and the propagator for these fields. \par In the next chapters we investigate different phenomenological implications. We start out in chapter \ref{chap:1} with a massive spin-3/2 field hidden in the standard model (SM) spectrum thanks to the form of the special interaction that vanishes when the field falls into the mass shell. Different collider signatures are investigated through analytical computations and numerical predictions. \par In chapter \ref{chap:2}, we assume that the Higgs boson stays stable via a finely tuned hidden sector which involves a spin-3/2 field that is split from the SM and whose sole contact with it at the renormalizable level is through the neutrino portal. Then, the total mass correction to the Higgs mass is used as a constraint to calculate the mass scale of the spin-3/2 field. \par Lastly, we investigate the possible role that a spin-3/2 field could play in leptogenesis. Our model incorporates a spin-3/2 field in addition to the type-I see-saw fields in inducing the CP asymmetry and mitigating the naturalness problem of the Higgs boson. We investigate the plausibility in regard to successful leptogenesis with no side effects, specifically the naturalness of the Higgs boson and correct prediction of the active neutrino masses.