This chapter reviews recent advances and ongoing challenges in the quality control of Azospirillum-based inoculants, which are increasingly used in agriculture for their plant growth-promoting properties and contribution to sustainable production systems. Emphasis is placed on the quality control, outlining how both internal and independent laboratory processes are essential to ensure viability, purity, and efficacy of inoculants throughout manufacturing, storage, and application. The chapter highlights the development and implementation of standardized protocols in countries such as Argentina, Uruguay, Brazil, and Colombia, including the adoption of innovative methodologies like the drop plate technique and molecular assays for strain identification. Advanced microscopy-based techniques (optical, SEM, and TEM) are discussed as powerful tools for the detailed characterization of Azospirillum morphology, viability, and contamination, enabling more accurate and reproducible quality assessments. The chapter also addresses agronomic efficiency evaluation, detailing both laboratory and field-based approaches and the key parameters used to measure inoculant performance, such as plant growth indices and nitrogen use efficiency. The impact of regulatory frameworks, country-specific requirements, and emerging trends in the development and deployment of Azospirillum-based inoculants are critically examined, with a focus on their implications for sustainability, productivity, and environmental stewardship in agriculture. This comprehensive overview underscores the need for ongoing research, harmonized standards, and interdisciplinary collaboration to advance the effective and safe use of microbial inoculants in global food systems.