Objectives: Emotional processing abnormalities have been implicated in bipolar disorder (BD) but studies are typically small and uncontrolled. Here, facial expression recognition was explored in a large and naturalistically recruited cohort of BD patients. Methods: 271 patients with BD completed the facial expression recognition task. The effects of current medication together with the influence of current mood state and diagnostic subtype were assessed whilst controlling for the effects of demographic variables. Results: Patients who were currently receiving treatment with lithium demonstrated significantly poorer accuracy in recognising angry faces, an effect that held in a monotherapy sub-analysis comparing those participants on lithium only and those who were medication-free. Accuracy in recognising angry faces was also lower amongst participants currently taking dopamine antagonists (antipsychotics). Higher levels of current depressive symptoms were linked to poorer accuracy at identifying happy faces. Conclusion: Use of lithium and possibly dopamine antagonists may be associated with reduced processing of anger cues in BD. Findings support the existence of mood-congruent negative biases associated with depressive symptoms in BD. Observational cohort studies provide opportunities to explore the substantial effects of demographic, psychometric and clinical variables on cognitive performance and emotional processing.