The current study was carried out to assess the effect of different soil moisture levels i.e., 20, 40, 60, 80 compare to 100% of soil field capacity (FC) and potassium fertilization (KF) on final nematode population (Pf) and reproduction factor (RF) of root knot nematode, Meloidogyne incognita on tomato plant, Solanum lycopersicum L. (cv. Elisa). Results showed that of 20, 40, 60% FC significantly decreased tomato growth parameters compared to 100% FC control treatment. Moreover, the results indicated that the Pf and RF were significantly decreased at soil moisture levels of 20,40,60 and 80 compared to 100% level. The 80% FC level caused minor reduction in fruit fresh weight while significantly reduced nematode infection parameters (Pf and RF) compared to 100% soil moisture level control treatment. On the other hand, application of K-fertilization at every soil moisture levels enhanced the increase in all tomato growth parameters and reduced all nematode infection parameters. All studied tomato plant physiological parameters i.e. relative water content (RWC), cell membrane stability (CMS) and chlorophyll content were decreased as a result of decreasing soil moisture levels from 100 FC to 20% FC. In contrary, results showed that proline content in tomato plants was increased due to the decrease of soil moisture levels. Thus, soil moisture levels of 80% FC or 60% FC combined with high application rate of potassium (96 kg/fed) can be used to manage root- knot nematode M. incognita infection without negative effects on tomato crop growth attributes.