Assessing the prevalence of anaemia, iron deficiency and iron deficiency anaemia among non-pregnant and pregnant women is essential for evidence-based intervention programs. The purpose of this prospective outpatient and community-based cross-sectional study was to assess the prevalence of those conditions among pregnant women resident in the National Capital District (NCD) and attending the Outpatient Antenatal Clinic in Port Moresby General Hospital. Blood samples were collected from 50 non-pregnant and 157 pregnant women who gave consent. HemoCue was used to measure haemoglobin; the serum ferritin, soluble transferrin receptor (sTfR) and C-reactive protein were measured by specialized 96-well enzyme-linked immuno-sorbent assay (ELISA) kits. The ‘sTfR-F index’ was calculated. Mild to moderate anaemia, low serum ferritin and elevated serum sTfR were found in 28% of the non-pregnant women; the sTfR-F index showed that 16% of them had iron deficiency anaemia. Among the pregnant women, 60% had mild to severe anaemia indicating severe public health significance; 48% had low serum ferritin and 38% had elevated serum sTfR; the sTfR-F index showed that 38% of them had iron deficiency anaemia. Mild to severe anaemia was present in 47%, 71% and 62% of the pregnant women in the first, second and third trimesters respectively, while iron deficiency anaemia was present in 20%, 53% and 48% of the pregnant women in the first, second and third trimesters respectively. The sTfR-F index showed that iron deficiency anaemia was present in 36% of primigravida and 40% of multigravida. Social mobilization, intensive and focused education, aggressive awareness campaigns, including all relevant target groups and policy makers, are required to effectively address this major public health issue.