The professionalism of Guidance and Counseling (BK) teachers is commonly understood within the framework of technical and academic competence. However, the effectiveness of counseling services in schools also depends on the continuously developing personal quality of the counselor, a dimension that has not received adequate attention in the discourse on the professional development of BK teachers in Indonesia. This study aims to analyze how personal development contributes to the professionalism of BK teachers in counseling services at senior high schools (SMA), while also identifying the challenges faced by BK teachers in carrying out their services. The study used a descriptive qualitative approach. Six BK teachers from public and private senior high schools across Lombok Timur Regency, members of the Guidance and Counseling Teacher Forum (MGBK) of SMA Lombok Timur, were selected as informants through purposive sampling. Data were collected through semi-structured written interviews complemented by field notes from observations of MGBK activities. Data were analyzed descriptively-qualitatively through data reduction, data display, and conclusion drawing. The results show that all informants have been involved in various forms of self-development, such as training, workshops, technical guidance, supervision, and active participation in the MGBK forum. This self-development had a positive impact on three aspects of BK teachers' professionalism, namely increased professional self-awareness, strengthened interpersonal competence, and reinforced professional integrity and ethics. On the other hand, BK teachers face a number of structural challenges, including misconceptions about the role of BK teachers among school members, student-to-counselor ratios far exceeding the ideal standard, high administrative burdens, the complexity of students' problems, and the demand to adapt to digital technology. This study confirms that counselors' personal development is an important foundation that sustains the quality of BK services, and that the MGBK forum plays a strategic role as a venue for the sustainable professional development of BK teachers in the region.