Background: Mixed depression (MxD) is narrowly defined in the DSM-IV and somewhat broader in the DSM-5, although both exclude psychomotor agitation as a diagnostic criterion. This article proposes a clinical description for defining MxD, which emphasizes psychomotor excitation. Methods: Two hundred and nineteen consecutive outpatients were diagnosed with an MxD episode using criteria proposed by Koukopoulos et al. [Acta Psychiatr Scand 2007;115(suppl 433):50-57]; we here report their clinical features and antidepressant-related effects. Results: The most frequent MxD symptoms were: psychic agitation or inner tension (97%), absence of retardation (82%), dramatic description of suffering or weeping spells (53%), talkativeness (49%), and racing or crowded thoughts (48%). MxD was associated with antidepressants in 50.7% of patients, with similar frequency for tricyclic antidepressants (45%) versus selective serotonin reuptake inhibitors (38.5%). Positive predictors of antidepressant-associated MxD were bipolar disorder type II diagnosis, higher index depression severity, and higher age at index episode. Antipsychotic or no treatment was protective against antidepressant-associated MxD. Conclusions: MxD, defined as depression with excitatory symptoms, can be clinically identified, is common, occurs in both unipolar depression and bipolar disorder, and is frequently associated with antidepressant use. If replicated, this view of MxD could be considered a valid alternative to the DSM-5 criteria for depression with mixed features.