Activation of C‐X‐C motif chemokine receptor 4 (CXCR4) has been reported to result in lung protective effects in various experimental models. The effects of pharmacological CXCR4 modulation on the development of acute respiratory distress syndrome (ARDS) after lung injury, however, are unknown. Thus, we studied whether blockade and activation of CXCR4 influences development of ARDS in a unilateral lung ischaemia–reperfusion injury rat model. Anaesthetized, mechanically ventilated animals underwent right lung ischaemia (series 1, 30 minutes; series 2, 60 minutes) followed by reperfusion for 300 minutes. In series 1, animals were treated with vehicle or 0.7 μmol/kg of AMD3100 (CXCR4 antagonist) and in series 2 with vehicle, 0.7 or 3.5 μmol/kg ubiquitin (non‐cognate CXCR4 agonist) within 5 minutes of reperfusion. AMD3100 significantly reduced PaO2/FiO2 ratios, converted mild ARDS with vehicle treatment into moderate ARDS (PaO2/FiO2 ratio<200) and increased histological lung injury. Ubiquitin dose‐dependently increased PaO2/FiO2 ratios, converted moderate‐to‐severe into mild‐to‐moderate ARDS and reduced protein content of bronchoalveolar lavage fluid (BALF). Measurements of cytokine levels (TNFα, IL‐6, IL‐10) in lung homogenates and BALF showed that AMD3100 reduced IL‐10 levels in homogenates from post‐ischaemic lungs, whereas ubiquitin dose‐dependently increased IL‐10 levels in BALF from post‐ischaemic lungs. Our findings establish a cause‐effect relationship for the effects of pharmacological CXCR4 modulation on the development of ARDS after lung ischaemia–reperfusion injury. These data further suggest CXCR4 as a new drug target to reduce the incidence and attenuate the severity of ARDS after lung injury.