This chapter explores the intricacies of rationalizing homogeneous catalysis using theoretical methods. The computational modeling of reactivity facilitated by homogeneous catalysts involves several stages, each presenting specific challenges that require the selection of the most suitable approach. A brief overview of commonly used methods, particularly ab initio and density functional theory (DFT), is provided, highlighting their respective accuracies, costs, and areas of applicability. Emphasis is placed on achieving a balance between methodological rigor and computational efficiency through multi-level approaches. Guidance is also offered to help researchers choose appropriate computational protocols that align with the experimental conditions encountered in homogeneous catalysis. In addition to its focus on homogeneous catalysis, this chapter serves as a practical guide for applying computational methods within the broader field of organometallic chemistry.