Phytosanitary problems drastically affect passion fruit cultivation around the world. Scab, a fungal disease that attacks the aerial part of plants, especially the younger leaves, impairs development and reduces plant productivity. The objective of this work was to evaluate the effect of treatment with a fungal cell wall glycoprotein, named pGM from peptidogalactomanann, in the control scab caused by Cladosporium hebarum infection. Under greenhouse conditions, morphological parameters or plant development were evaluated in two passion fruit genotypes, ‘H09-110/111’ and ‘FB300’. pGM treatment was able to mitigate the damage caused to plant development in parameters such as height, the number of leaves, stem diameter, leaf area and biomass in the ‘H09-110/111’ genotype compared to the control. However, in the genotype ‘FB300’, no significant differences were observed concerning the control. Passion fruit scab disease incidence and severity were also reduced by pGM treatment. Therefore, this study suggests that the use of pGM can lead to control and attenuation of the damage caused by this fungus in the early stages of passion fruit plants ‘H09-110/111’ when the plants are more susceptible to biotic stresses.