As one of the worst invasive alien plant species in China, Ageratina adenophora has caused serious economic losses and reduced the diversity of native species, possibly due to allelopathic interactions. However, we have little knowledge of its effects on ferns. In Petri dish bioassays, the effects of the aqueous leachates from roots, stems and leaves of A. adenophora on spore germination and gametophyte development of Neocheiropteris palmatopedata were investigated. All leachates inhibited spore germination and rhizoid growth of N. palmatopedata. Furthermore, the inhibitory effects increased with increasing leachate concentrations, and root leachates exhibited the greatest inhibition. Possible inhibitory causes are discussed in the present study. Additionally, the gametophytes of N. palmatopedata treated with the leachates of A. adenophora did not show morphological differences compared with the control. This result differs from previous studies investigating morphological changes in other fern species when associated with A. adenophora. Varying sensitivity of different fern species to the same allelochemicals of A. adenophora may partly be responsible for this difference.