Jacaranda ulei Bureau & K.Schum., Bignoniaceae, is an evergreen shrub used to treat skin diseases, rheumatism, urinary tract disorders, and dysentery. This study aimed to perform a morphoanatomical study of J. ulei and analyse the composition and chemical variability of the volatile oils from its leaves over 11 months. The identification of the volatile oil components from the leaves was performed by gas chromatography coupled with mass spectrometry (GC-MS). The major chemical components of the volatile oils from the leaves were γ-amorphene (1.3-27.1%), n-heneicosane (0.4-59.5%), ethyl hexadecanoate (0.4-8.1%), eicosane-3-phenyl (0.9-18.5%), squalene (March-66.4%, May-8.3%, August-17.6%, September-0.64%, and November-6.47%), and 9-octadecenamide (50.9% in the June sample). Two clusters were identified: one was characterized by the vegetative period and the other by the flowering period of the species, showing that the chemical compounds of the volatile oils varied according to phenological factors. The anatomical description contributed to the taxonomic identification of the species. This is the first report on the volatile oil obtained from J. ulei