Anaemia disproportionately affects women of reproductive age in sub-Saharan Africa including Nigeria. Yet, community-based studies on the prevalence and determinants of anaemia among women of reproductive age are scarce in Nigeria. A cross-sectional community-based survey using a nationally representative sample. This study described anaemia prevalence and its associated factors among women of reproductive age, pregnant women, and non-pregnant women in Nigeria. We analysed data from the 2018 Nigeria Demographic and Health Survey. Pregnant women with a haemoglobin level less than 11 g/dL and non-pregnant women with a haemoglobin level less than 12 g/dL were considered anaemic. Anaemia was also categorized as mild, moderate, and severe. Pearson's chi-square test was used to evaluate the association between anaemia status and independent variables. All variables with ρ ⩽ 0.25 in bivariate analyses were further analysed using complex sample logistic regression. Anaemia prevalence was 57.8%, 57.4%, and 61.1% for women of reproductive age, non-pregnant women, and pregnant women, respectively. The prevalence of severe anaemia was 1.6%, 1.5%, and 2.3% for overall women of reproductive age, non-pregnant women, and pregnant women, correspondingly. The southern regions, rural residence, low education, unemployment, low wealth index, and non-use of modern contraceptives significantly increased the likelihood of anaemia and severe anaemia among women of reproductive age and non-pregnant women. The likelihood of being anaemic was significantly increased by large family size among women of reproductive age and by being underweight among non-pregnant women. The South-East region, rural residence, low education, and unemployment were significantly associated with anaemia among pregnant women. The South-South region and unemployment increased the likelihood of severe anaemia among pregnant women. Short stature significantly reduced the odds of being anaemic and severely anaemic among pregnant women. Anaemia prevalence among all categories of women of reproductive age is high in Nigeria. Predictors of anaemia prevalence and severity should be considered in policies intended to reduce anaemia among women of reproductive age in Nigeria.