Abstract Background Studies investigating associations between mammographic density (MD) and breast cancer subtypes have generated mixed results. We previously showed that having extremely dense breasts was associated with the HER2-enriched subtype in Chinese breast cancer patients. Methods In this study, we re-evaluated the MD-subtype association in 1,549 Chinese breast cancer patients, using VolparaDensity software to obtain quantitative MD measures. All statistical tests were two-sided. Results Compared to women with luminal A tumors, women with luminal B/HER2- (odds ratio [OR]=1.20, 95% confidence interval [CI]: 1.04-1.38, p = 0.01), luminal B/HER2 + (OR = 1.22, 95% CI: 1.03-1.46, p = 0.03), and HER2-enriched tumors (OR = 1.30, 95% CI: 1.06-1.59, p = 0.01) had higher fibroglandular dense volume. These associations were stronger in patients with smaller tumors (<2cm). In contrast, the triple negative subtype was associated with lower non-dense volume (OR = 0.82, 95% CI: 0.68-0.99, p = 0.04), and the association was only seen among older women (>50 years old). Conclusion Although biological mechanisms remain to be investigated, the associations for the HER2-enriched and luminal B subtypes with increasing MD may partially explain the higher prevalence of luminal B and HER2+ breast cancers previously reported in Asian women.