Purpose: The purpose of this paper is to provide a comprehensive description and analysis of quality levels with regard to dual Vocational Education and Training (VET) at companies participating in this programme in Spain, with a specific focus on company size. Design/methodology/approach: The study is based on a quantitative cross-sectional analysis, collecting quality indicator data from 829 participating companies through a structured questionnaire. Subsequently, both descriptive and inferential analyses were conducted to address the specific objectives. Findings: The study reveals that, on the whole, companies implement dual VET with a high level of quality, achieving compliance rates of above 70% in dimensions related to process, resources, staff and training. However, in this study the dimensions of evaluation and synergies showed lower compliance rates, with figures of 47.4 and 25.7%, respectively. Notably, medium-sized and large companies outperformed micro-SMEs and SMEs in training, evaluation and synergies, while SMEs surpassed large companies in resource management. The study provides recommendations for enhancing dual VET in companies. Research limitations/implications: The main limitations of this study pertain to an absence of data concerning the distribution of the population by company sizes and a lack of information regarding the specific sectors to which these companies belong. Originality/value: This study offers significant value, as it provides data on the quality of dual VET in companies considering size as a key factor. These findings are particularly noteworthy given that research on the quality of dual VET in companies remains limited within the scientific literature.