The new mass-rearing facility of Mexico’s Moscamed Program, currently under construction, has been projected to produce up to 1000 million sterile male pupae per week of the Ceratitis capitata Vienna 8 strain. Given the slower development of females of this strain, the starter-finalizer larval diet system was proposed to sustain the biological amplification of female-male colonies. To start operations in the new facility, a suitable novel larval diet formulation with this system had to be determined. In this study, several starter-finalizer larval diet formulations were designed and evaluated in two stages. In the first stage, eight novel diet formulations were designed using the standard ingredients of mass rearing operations. Larval recovery, larval weight, development speed, and temperature profile were determined in these diets using the male-only stream (thermally treated eggs). The two best diets were further evaluated in the second stage. An additional adjusted diet formulation and the standard mass rearing diet were also included in this stage. In this second stage, larval recovery, larval weight, temperature profile, and microbiological and physicochemical properties of the larval diets were evaluated using the male and female streams. Based on productivity, quality, and development speed, two out of eight larval diets were further evaluated in the second stage. Of the four diets included in the second stage, the formulation “T5-N3” presented the best balance between productivity and quality: a good development time, a stable productivity, an optimal thermal performance, and a relatively better suppression of fungal and bacterial development. The formulation “T5-N3” was determined as the best option for initiating the mass rearing of Vienna 8 colonies at the new facility of Mexico’s Moscamed Program. Nevertheless, this formulation still needs to be optimized. Most importantly, mass-rearing biofactories have to be prepared for the continuous improvement of larval diets. Future directions for the optimization and design of larval diets for large-scale operations are discussed.