Abstract: Pure methanol (m) and methanol water (mw) extracts of 5 plants namely: peppermint, eucalyptus, lavandula, Russian knapweed and datura were screened for their antifungal ability against Alternaria alternata, the causal agent of Alternaria leaf spot of potato at 5, 10 and 15% concentrations in vitro. Fungicide mancozeb 0.2% was also used for better comparison. Poisoned food technique and spore germination assay method were used to evaluate the antifungal efficacy of plant extracts. Present findings showed that methanol extracts of eucalyptus, peppermint and lavandula had impressive antifungal effects in inhibiting the mycelial growth as well as spore germination of the pathogen. It was also found that methanol extracts were quite more effective than methanol water extracts in this regard. Methanol extracts of peppermint (15%), lavandula (15%), peppermint (10%) and eucalyptus (15%) demonstrated promising ability in inhibiting the mycelial growth of A. alternata by 0.13, 0.40, 0.43 and 0.50 cm, mycelial growth respectively, while majority of methanol water extracts had either less or no effects in this connection. Spore germination of A. alternata was prominently reduced by methanol extracts, while those of methanol water extracts had very less effects in this regard. Mancozeb (0.2%), methanol extracts of eucalyptus (15%) and peppermint (10%) by 2, 6 and 7% spore germination were best, while methanol water extracts of datura 10, 15 and 5%, lavandula 15 and 10% and also Russian knapweed 5% represented no effect and by 91, 89, 87, 87, 85 and 85% spore germination were at par with control. Findings from this study confirmed that plant extracts can be used as less hazardous natural fungicides in controlling plant pathogenic fungi, thus reducing the dependence on the synthetic fungicides. Methanol extracts of peppermint, eucalyptus and lavandula might be promising materials for natural formulations in controlling Alternaria leaf spot of potato in the field.