The present study reports the results of gas chromatographic-mass spectrometric (GC/MS) analyses of the essential oils from the aerial parts of Ballota nigra L. ssp foetida (Lamiaceae) collected at flowering and fruiting times, as well as their in vitro antifungal activity against nine plant pathogenic fungi. Moreover, the essential oils were evaluated for their antifungal activity using the agar dilution method, and also MICs (minimum inhibitory concentrations) and MFCs (minimum fungicidal concentrations) were determined. The major compounds identified in the flowering and fruiting aerial parts oils respectively were beta-caryophyllene (22.6% and 21.8%), caryophyllene oxide (18.0% and 20.5%) and germacrene-D (16.5 and 13.1%). The oils showed in vitro antifungal activity against some species of Fusarium, Botrytis cinerea, and Alternaria solani. Our study indicates that the oil of B. nigra ssp foetida could be used as a control agent for plant pathogenic fungi in natural formulations.