Campomanesia sessiliflora (O.Berg) Mattos is a Brazilian native plant species used in a popular medicinal tea for treating gastrointestinal, urinary, and dermatological pathologies. This study evaluated the toxicity of Campomanesia sessiliflora (O.Berg) Mattos via acute and subacute toxicity tests. It also analyzed mutagenic and genotoxic potentials by the micronucleus test, which detects genetic material damage indicating mutagenicity, and the comet assay, which assesses DNA damage levels as a genotoxicity indicator. The plant extract initially originated from the ultrasonic maceration of Campomanesia sessiliflora (O.Berg) Mattos leaves in a hydroethanolic solution. The involved animals were adult Wistar rats. Ten females were available to evaluate acute toxicity and estimate the LD50, receiving a dose of 2000 mg/kg. The subacute toxicity evaluation used 35 females and 35 males divided into seven groups: negative control (saline control – SC), positive control (cyclophosphamide control – CC), 125 mg/kg (125), 250 mg/kg (250), 500 mg/kg (500), 1000 mg/kg (1000), and the satellite group (ST). Genotoxicity and mutagenicity experiments applied bone marrow micronucleus and comet assays. Acute and subacute toxicity tests did not present behavioral, physical, and physiological changes (p≥0.05). Administering the Campomanesia sessiliflora (O.Berg) Mattos extract reduced spleen size in male and female animals, without histopathological changes. However, doses above 500 mg/kg showed significant genotoxic and mutagenic effects in the comet and micronucleus assays compared to the control group. The extract did not exhibit acute or subacute toxicity, but doses higher than 500 mg/kg indicated some level of genotoxicity and mutagenicity.