Arabidopsis thaliana transgenic plants expressing the mannose binding lectin GNA from snowdrop (Galanthus nivalis), under the control of the constitutive 35S promoter of the Cauliflower Mosaic Virus (CaMV) with an enhancer sequence were produced. They were used to investigate the potential of this lectin to control the root-knot nematode Meloidogyne incognita. Homozygous lines expressing GNA in roots at an estimated range of 0.1–1.3% of total soluble proteins were selected. Protection against root-knot nematodes was investigated in an in vitro test. Some lines had a significant decrease (20–50%) in root gall number. However, one line showed a higher gall number compared to the control line. This effect, which is not correlated to GNA protein root level, suggests a complex action mechanism of lectin against nematodes. Nevertheless, GNA seems to have a strong potential against M. incognita and could be used as a component of integrated pest management programs