Pasture-based production systems are predominant in major beef-producing countries, however, these systems lack validated protocols to assess animal welfare under commercial conditions. The objective of this study was to validate an animal welfare protocol for fattening Zebu cattle farms in tropical pasture systems. The initial protocol was developed with the participation of producers, professionals, the general public, and the Colombian health authority, through workshops with a participatory approach and collaborative knowledge management. The validation was carried out in 24 pasture-based commercial Zebu cattle farms in the middle Magdalena region of Colombia. Visits were made with an average duration of 2.5 hours, which included the evaluation of 788 fattening cattle. The protocol evaluated animal-based, resource-based, and livestock management indicators through a questionnaire-guided interview to evaluate cattle handling and health, animal-based measurements, and documentation management. A protocol validation process was carried out by selecting indicators that remained unchanged, adjusting those that were feasible to implement, and eliminating inadequate or unnecessary indicators. The application of the protocol demonstrated that there are valid and feasible measures to include in the evaluation protocols of pasture-based fattening systems. Likewise, the active participation of producers is crucial to achieving a greater commitment to the implementation of this protocol.