Toxoplasma gondii (T. gondii) causes a life-threatening opportunistic infection. Despite its clinical importance, very few therapeutic drugs against T. gondii are available. Furthermore, these therapeutic regimens are not always suitable for prolonged treatment due to adverse side effects as well as the potential of clinical failure by selecting drug-resistant parasite variants. Dictamnus dasycarpus is known to have many medicinal properties, including anti-inflammatory, anti-fever, and anti-rheumatic activities. In this study, 70% ethanol extract of Dictamnus dasycarpus showed anti-T. gondii effects. Ethanolic extracts of Dictamnus dasycarpus used to treat T. gondii were tested in vitro for their anti-T. gondii activity and cytotoxicity. The selectivity of Dictamnus dasycarpus extract was 7.52, which was higher than that of Sulfadiazine (2.08). We conducted an in vivo animal test to evaluate the anti-T. gondii activity of Dictamnus dasycarpus extract as compared with that of Sulfadiazine. In T. gondii-infected mice, the inhibition rate of Dictamnus dasycarpus extract was high, similar to that of Sulfadiazine. This indicates that Dictamnus dasycarpus extract may be a source of new anti-T. gondii compounds.