Purpose: The primary objective of this open-label, retrospective, observational study was to examine change in indicators of anxiety changed after treatment period of at least 1 month with the homeopathic-complex medicine Datif-PC®. A secondary objective was to describe the quantitative changes in the sleep pattern of the subjects included in the study.Methods: The study population consisted of 71 subjects suffering from mild to moderate anxiety, who were treated with a homeopathic-complex medicine. The subjects had attended at least 2 consultations during the year 2010, with the second visit taking place at least 30 days after the first baseline visit. At both visits, subjects were administered the State-Trait Anxiety Inventory (STAI)-Y questionnaire (consisting of trait and state subscales) to assess their level of anxiety. Sleep quality was assessed based on the subjects’ self-reported number of hours slept and number of night-time awakenings, before and after treatment.Results: Compared to baseline, the average (STAI)-state score at visit 2 decreased by more than 6 points, while the STAI-trait score decreased by more than 3 points. This was statistically significant (p < 0.0001) for both subscales. These findings were stable in subgroup analyses (gender, age and anxiety level). The average number of hours slept per night increased significantly at visit 2 compared to baseline (from 5.1 ± 1.1 to 5.56 ± 0.9 h, p < 0.0001). A marked decrease in the average number of night-time awakenings was also observed at the second visit (−42%, p < 0.0001).Conclusions: This retrospective observational study suggests that treatment of anxiety and sleep disorders with Datif-PC® can produce notable improvements even in a short period of time. Furthermore, the observed effects were not affected by sex, age or baseline anxiety. Further controlled, randomized studies are justified.