Objectives Although ethnic minority clients (EMs) from STI endemic countries have a higher risk for STI, little is known about their STI clinic consultation rate proportionality. The aim of this study was to assess consultation and chlamydia positivity rates among different EMs visiting STI clinics in the Netherlands. Methods We calculated consultation rates in EM groups by dividing the number of STI consultations by the total number of inhabitants in the region belonging to an EM, then compared the EM rates to native Dutch rates. Factors associated with chlamydia positivity were analysed using multivariate regression analysis. Results A total of 23,841 clients visiting an eastern Netherlands STI clinic between 2011 and 2013 were included in the analysis, of which 7% were EMs. The consultation rate of native Dutch clients was 22.5 per 1000, compared to 8.5 per 1000 among EMs. Consultation rates in all EMs were lower than in Dutch clients, except for Antillean or Aruban EMs and Latin American EMs. The chlamydia positivity rate among all clients was 15.5%, and Antillean or Aruban ethnicity (27.1%) EMs had the highest rates. Multivariate analysis identified the following factors associated with chlamydia positivity: Eastern or Northern European EM, African EM, Antillean or Aruban EM, STI related symptoms, heterosexual preference, partner in a risk group, receiving a partner notification, and having had three or more partners in the past six months. Conclusion On a population level, most EMs visit STI clinics less often than native Dutch clients, but they have a higher rate of positive chlamydia diagnoses. STI clinics should increase outreach activities for EM clients because they are insufficiently reached by current practices, but contribute substantially to chlamydia incidence rates.