Rice is the staple food and the most important agricultural crop in Cambodia, yet yields remain constrained by a range of biotic and abiotic stresses. Among these, the root-knot nematode Meloidogyne graminicola (M. graminicola) is a major soil-borne pest that causes considerable rice yield losses across Asia, including Cambodia. Sustainable and environmentally friendly management approaches are therefore essential, with resistant cultivars recognized as one of the most reliable strategies for long-term nematode control in heavily infested areas. This study evaluated the susceptibility of 37 rice cultivars cultivated in Cambodia to M. graminicola infection, with the highly susceptible cultivar IR64 included as a positive control. Plants were grown under controlled conditions and inoculated with 100 second-stage juveniles (J2) isolated from Cambodian rice fields. Nematode counts after one week post-inoculation provided a preliminary assessment of susceptibility, after which nine of the least susceptible cultivars were reinoculated with 140 J2 to evaluate reproduction factors. The results showed that six cultivars exhibited moderate susceptibility, three were susceptible, and IR64 was highly susceptible to M. graminicola. None of the evaluated cultivars demonstrated complete resistance, and nematode penetration and development were observed within roots as early as one day post-inoculation, highlighting the aggressiveness of the pest. These findings indicate that resistant germplasm is absent among the tested Cambodian rice cultivars, underscoring the urgent need for targeted breeding programs to incorporate nematode resistance. Such efforts will be essential to strengthen sustainable rice production and contribute to long-term food security in Cambodia.