Consanguineous marriage is preferred in many countries, especially by Muslims. Despite the increasing education rate in Saudi Arabia, the prevalence of consanguineous marriage does not seem to be decreasing as quickly as expected. The present study aimed to investigate the current prevalence of consanguineous marriage among educated married adults in Riyadh and to determine the factors favouring it. The cross-sectional study was conducted in 2017–18 using an online questionnaire. A total of 550 questionnaires were sent to married adults of both sexes and 417 responded, giving a response rate of 75.8%. The questionnaire consisted of two parts: the first section asked for demographic data such as age, sex, educational level, residential area and family size. The second part was about consanguineous marriage and its degree if present, family history of consanguineous marriage and level of awareness of its potential negative impact on offspring. It was found that the prevalence of consanguineous marriage among the participating educated adults was 39.8% and most of these were married to a first cousin. Neither level of education nor age affected the likelihood of consanguineous marriage, but predictors for the practice among the educated participating adults were having a family history of consanguineous marriage, having consanguineous parents and having a personal preference for consanguineous marriage.