Botrytis blight, caused by Botrytis cinerea infection, is the most significant fungal disease in Geraldton waxflower (Chamelaucium uncinatum). Paclobutrazol, a gibberellin biosynthesis inhibitor, is often used with potted ornamental plants to control their growth and provide more compact plants. Paclobutrazol falls within a group of chemicals classed as triazoles, which have been recommended for use as both fungicides and plant growth regulators. It was, therefore, thought that paclobutrazol might be effective in the control of B. cinerea in plants. To this effect, paclobutrazol (0, 0.05, 0.25, 1.25 and 6.25 mg per dish) was added to dishes containing B. cinerea isolated from C. uncinatum plants collected in south-east Spain, and the inhibition of growth was studied in vitro. The effect of a gibberellic acid spray (346 mg/L) on fungal growth and its interaction with paclobutrazol was also studied. All five doses of paclobutrazol tested decreased fungal growth in a dose-dependent manner, reducing the size of the conidia and the number of sclerotia. The highest paclobutrazol dose eliminated conidiation, completely inhibited the formation of sclerotia and provoked irreparable injuries in the mycelium. Gibberellic acid did not affect fungal growth but the number of sclerotia increased with this hormone.