Resistance to root-knot nematode (Meloidogyne spp) has been identified, incorporated, and deployed in Kutsaga commercial cultivars of tobacco, Nicotiana tabacum. These cultivars have varying resistance levels to root-knot nematode. The classification of the varieties was based on root gall indices obtained at final reaping, after the varieties have been grown in fields with high nematode populations. However, little is known about the mechanism of root-knot nematodes resistance in local tobacco varieties. The objective of this study, therefore, was to determine the nature of root-knot-nematode resistance in the Kutsaga root-knot resistant varieties. Trials were conducted in the greenhouse to investigate the role of tobacco root diffusates in the hatching and survival of infective juveniles, the rate of penetration and development of root-knot nematodes in test varieties. Six tobacco varieties (K RK26, K RK29, K RK66, T71, T72 and K RK64) with moderate to high resistance to root-knot nematode were used in the study. A known root-knot nematode susceptible cultivar K M10 was included as a control. Results showed that root diffusate had no inhibitory or delaying effect on hatching and survival of infective juveniles and the tested tobacco varieties deployed different mechanisms of resistance. These included the suppression of root penetration by infective juveniles and the inhibition of development and reproduction of the nematodes after penetration. These results are discussed in detail in this paper.