Chlamydial respiratory tract infections are associated with the development and exacerbation of asthma in both children and adults, but the mechanisms underpinning this association remain unknown. We investigated the effect of the age of chlamydial infection on key features of asthma in later life using mouse models of Ovalbumin-induced allergic airways disease (AAD). Neonatal and infant, but not adult infection resulted in differential and permanent alterations in airway eosinophils, T-cell cytokines and dendritic cells (DCs). Infection of neonates suppressed eosinophil influx into the airways and reduced T-cell cytokine release which correlated with a significant reduction in the number and activation of DCs. In stark contrast, infant infection augmented eosinophil influx and increased T-cell cytokine release which correlated with increased DC numbers and activation. Importantly, both neonatal and infant infections enhanced physiological (mucus secreting cell hyperplasia and airways hyper-responsiveness) responses in AAD in later life, which correlated with enhanced IL-13 expression in the lung. Furthermore, neonatal infection induced substantial alterations in lung structure which was linked with increased TGF-β in lung tissue. Thus, early life infection enhances pivotal features of AAD through age dependent, differential affects on immune responses and lung structure.