The optimal age for introducing complementary feeding to breast-fed infants may differ depending on the setting. Prolonged exclusive breast-feeding (EBF) protects against infection but may increase the risk of iron deficiency (ID)/anaemia (IDA) in vulnerable infants. The aim of the present study was to compare haemoglobin (Hb), serum ferritin (SF), anaemia (Hb < 11 g/L), ID (SF < 12 μg/L) and IDA (Hb < 10.5 g/dL + Hct < 33% + ID) using observational analyses in 6-month old infants from Bogota, Colombia who were EBF for 4 to 5 versus 6 months or older, and examine predictors.Infant feeding was recorded, anthropometry performed, and blood obtained for Hb and SF at 6 months in healthy term infants (birth weight > 2500 g), all EBF for ≥4 months.One hundred eight infants (54% boys) were recruited; 46% EBF for 4 to 5 months, 54% EBF at 6 months. Prevalence of anaemia, ID, and IDA was 20%, 10%, and 5%, with no significant difference between EBF4-5 and EBF6 groups. In multivariate models, anaemia/ID were predicted by greater weight gain from 0 to 6 months, and anaemia also by caesarean delivery; Hb was lower in infants with higher intake of cows' milk; SF was lower in boys and those with greater weight gain. EBF4-5 versus EBF6 was not a significant predictor of any outcome.Anaemia and ID were common at 6 months but were not affected by EBF for 4 to 5 versus 6 months, suggesting 6 months EBF is safe in this population. Further research is, however, required to examine effects on later iron status. The findings highlight the need to emphasise avoidance of cow's milk before 12 months.