PurposeThis study investigates the impact of a buyer-assisted quality intervention on suppliers' quality performance and buyer–supplier relational dynamics in the garment industry.Design/methodology/approachThis study employed a multiple-embedded case study following a qualitative research approach. The study used data from buyer-assisted quality interventions in sewing lines of four garment supplier factories. Qualitative data were collected through semi-structured interviews of buyer's representatives at their office and senior managers, line inspectors, supervisors and workers in supplier factories. In addition, data related to product quality was obtained from quality check sheets and observations on the shop floor. Data were analysed using qualitative data analysis techniques.FindingsThis study demonstrates that a buyer-assisted quality intervention improves product quality performance by reducing quality defects in targeted garment products resulting in improved buyer–supplier relationships. Moreover, this study identifies the lack of a systematic approach in quality control as a key reason for poor product quality.Research limitations/implicationsThe study adds knowledge to the literature on quality improvement and buyer–supplier relationships by analysing buyer-assisted quality interventions in the garment industry in Bangladesh. The study demonstrates that buyer's assistance and adopting a systematic approach in quality control can significantly improve product quality in the garment industry.Practical implicationsThis research can help the quality assurance managers in buyer and supplier firms understand the significance of quality interventions and systematic quality control approach to decrease product quality defects and ensure smooth buyer–supplier relationships.Originality/valueThe study adds new knowledge on the link between buyer-assisted quality interventions, systematic quality control and product quality in garments factories in Bangladesh.