Currently, mammalian cell technology has become the focus of biopharmaceutical production, with strict regulatory scrutiny of the techniques employed. Major concerns about the presence of animal-derived components in the culture media led to the development of serum-free (SF) culture processes. However, cell adaptation to SF conditions is still a major challenge and limiting step of process development. Thus, this study aims to assess the impact of SF adaptation on monoclonal antibody (mAb) production, identify the most critical steps of cell adaptation to the SF EX-CELL medium, and create basic process guidelines. The success of SF adaptation was dependent on critical steps that included accentuated cell sensitivity to common culture procedures (centrifugation, trypsinization), initial cell concentration, time given at each step of serum reduction, and, most importantly, medium supplements used to support adaptation. Indeed, only one of the five supplement combinations assessed (rhinsulin, ammonium metavanadate, nickel chloride, and stannous chloride) succeeded for the Chinese hamster ovary-K1 cell line used. This work also revealed that the chemically defined EX-CELL medium benefits mAb production in comparison with the general purpose Dulbecco's Modified Eagle's Medium, but the complete removal of serum attenuates these positive effects.