This study investigates the impact of customer willingness to communicate in a second language on the development of employee language skills, with employee oral communication aspiration as a mediator. Additionally, it explores the moderating roles of customer retention management and consumer brand relationship quality in these relationships. The research aims to provide insights into how service-based businesses can leverage second-language communication to enhance employee skill development and customer relations. A quantitative research approach was employed, with data collected from 194 customers and 127 employees of service-based businesses where second-language communication is frequent. Standardized scales were adopted from past research, and SPSS was used for data analysis, including descriptive statistics, reliability tests, correlation analysis, regression, mediation, and moderation analysis. Multilevel modeling (MLM) was applied to analyze dyadic data. The results indicate that customer willingness to communicate in a second language significantly enhances employee oral communication aspiration, which in turn improves the development of language skills. Mediation analysis confirms that employee oral communication aspiration partially mediates this relationship. Additionally, customer retention management and consumer brand relationship quality moderate these effects, strengthening the relationships under high levels of management and brand connection. This study extends the service communication and employee development literature by highlighting the role of customer-employee language interactions in skill enhancement. The findings offer practical insights for businesses, emphasizing the strategic importance of fostering second-language communication to enhance employee competencies and customer engagement.