Recently, multi walled carbon nanotubes (MWCNTs) are gaining attention in the field of agriculture as advanced approaches to minimize toxicity of mycotoxins for crop plants. We examined whether MWCNTs can be used to alleviate genotoxicity and DNA damage induced by ochratoxin A (OTA) in the common bean (Phaseolus vulgaris) by comparing the action of three OTA doses, prior and post-adsorption of OTA on the surface of MWCNTs. The phenotypic parameters, ultrastructure of chloroplasts and nuclei using transmission electron microscopy, and status of nuclear DNA (nDNA) using flow cytometry, comet assay and random amplified polymorphic DNA (RAPD) were used as bioassays. Exposure time was 48 hours. The most effective MWCNT dose (optimal) was 50μg/mL; it enhanced the phenotypic parameters (seed germination and seedling growth, tolerance, and vigor indices), induced unexpected modification of size, shape, external and internal ultrastructure of chloroplasts and nuclei, increased the content of nDNA and genome size, reduced the extent of nDNA damage, and produced a larger number of amplified DNA products and new DNA bands more than the control. Lower and higher MWCNT doses had reductions in these parameters. On the other hand, increases in doses in OTA treatments induced major toxicity in the common bean, leading to strong reductions in all parameters of the bioassays. The MWCNTs served as an adsorbent for OTA and led to alleviation of its toxicity. We conclude that optimal and adsorbent MWCNTs could be used as nanocarbon-fertilizer and nanocarbon-mycotoxin to protect crop plants in order to increase crop quality and productivity.