The present study aimed at evaluating the antibacterial activity of essential oils (EOs) obtained from the leaves of two Iryanthera ulei individuals, popularly known as ucuubarana. The EOs were obtained by hydrodistillation made with leaves collected for 15 times from the same individual trees, resulting in two sets named 10EO and 15EO. Yields showed a seasonal variation to individual #10, although no variations between both #10 and #15 individuals have occurred. EOs were analyzed by gas chromatography/mass spectroscopy (GC/MS) before evaluation against Staphylococcus aureus ATCC29213, to obtain the minimal bactericidal concentrations (MBC). Principal component and canonical correlation analyses, PCA and CCA, were applied to ordinate the EOs and to correlate compounds, MBCs and seasonality. Major compounds, spathulenol α-cadinol, globulol and 1,10-di-epi-cubenol, together with isospathulenol, torreyol, viridiflorol and (Z)-nerolidol, commonly occurred in all EOs. PCA ordinated the essential oils obtained in the DS from both 10EO and 15EO sets. The set named 10EO was significantly more active against S. aureus than the 15EO set. The set named 10EODS, obtained from the leaves collected in the DS, was more effective against the pathogen and that the occurrence and percentage variation of (Z)-nerolidol, globulol and viridiflorol were significant to the antibacterial activity, despite the importance of the other common terpenes.