The effects of the lichenicolous fungus Heterocephalacria bachmannii on the antimicrobial potential of the lichen Cladonia foliacea demonstrated that the extracts investigated have antimicrobial potential against gram-positive and negative bacteria, and yeast, and inhibit the germination of fungal spores. Inhibition activity varied considerably depending on the extract, the bacterial species, and the absence or presence of H. bachmannii; unparasitised C. foliacea has a higher antimicrobial activity. Methanol and acetone extracts of C. foliacea alone have higher inhibition diameters than C. foliacea with H. bachmannii against Enterobacter cloacae; the methanol extract of C. foliacea showed the best inhibition (250 µg/ml). C. foliacea also has a high lysozyme potential against Streptococcus agalactiae and Staphylococcus aureus. Fungal hyphae of Alternaria alternata were more affected by the methanol extract from C. foliacea.