Research has shown that in groups of increasing age, religiousness becomes more prevalent. However, centenarians have only to a very limited extent been included in studies. The aim of this study is to characterize religious beliefs and practices in a larger sample of centenarians than have before been included in research on the matter. Using the Danish Civil Registration System, all individuals turning 100 in 2015 in Denmark were invited to participate (N = 498); 364 participated (73%) (82% women). Descriptive statistics on the centenarians’ self-reported belief, frequency of prayer and attendance at service were compared to the Danish general population. Associations between religious measures and age were examined using multivariable logistic regressions, controlling for sex and region. Centenarians more often reported being believers, praying and attending religious service, compared to all other age groups. Age, gender and region were all significant predictors of religiousness. The results of this study add to the body of the literature on religiousness and ageing, but extend it by including older age groups than have before been investigated. These findings warrant further investigations into the role of belief in this group and how it relates to mental health.