Over the last years, the interkingdom microbial interactions concerning bacteria and fungi cohabiting and/or responsible for human pathologies have been investigated. In this context, the Gram-negative bacteriumPseudomonas aeruginosaand fungal species belonging to theScedosporium/Lomentosporagenera are widespread, multidrug-resistant, emergent, opportunistic pathogens that are usually co-isolated in patients with cystic fibrosis. The available literature reports thatP. aeruginosacan inhibit the in vitro growth ofScedosporium/Lomentosporaspecies; however, the complex mechanisms behind this phenomenon are mostly unknown. In the present work, we have explored the inhibitory effect of bioactive molecules secreted byP. aeruginosa(3 mucoid and 3 non-mucoid strains) onS. apiospermum(n= 6 strains),S. minutisporum(n= 3),S. aurantiacum(n= 6) andL. prolificans(n= 6) under cultivation in a cystic fibrosis mimic environment. It is relevant to highlight that all bacterial and fungal strains used in the present study were recovered from cystic fibrosis patients. The growth ofScedosporium/Lomentosporaspecies was negatively affected by the direct interaction with either mucoid or non-mucoid strains ofP. aeruginosa. Moreover, the fungal growth was inhibited by the conditioned supernatants obtained from bacteria-fungi co-cultivations and by the conditioned supernatants from the bacterial pure cultures. The interaction with fungal cells induced the production of pyoverdine and pyochelin, 2 well-known siderophores, in 4/6 clinical strains ofP. aeruginosa. The inhibitory effects of these four bacterial strains and their secreted molecules on fungal cells were partially reduced with the addition of 5-flucytosine, a classical repressor of pyoverdine and pyochelin production. In sum, our results demonstrated that distinct clinical strains ofP. aeruginosacan behave differently towardsScedosporium/Lomentosporaspecies, even when isolated from the same cystic fibrosis patient. Additionally, the production of siderophores byP. aeruginosawas induced when co-cultivated withScedosporium/Lomentosporaspecies, indicating competition for iron and deprivation of this essential nutrient, leading to fungal growth inhibition.