This study aimed to assess the outcomes of nonsurgical therapy of chronic periodontitis patients performed by undergraduate dental students at King Saud University. Subjects who were >18 years old and had severe or moderate chronic periodontitis were eligible for the study. 33 patients constituted the study sample and received nonsurgical periodontal therapy by undergraduate students who were supervised by experienced periodontists. At reevaluation and maintenance visits, the mean values of plaque and gingival bleeding indices were significantly improved (PI; p < 0.01, BOP; p < 0.001), the mean number of teeth and tooth sites with probing pocket depth <5mm were significantly increased (p <0.01) whereas the mean number of those with ≥5 mm probing pocket depth were significantly decreased (P <0.001). No significant difference was reported in the number of teeth at reevaluation and maintenance visits in comparison to the initial examination. It was concluded that nonsurgical periodontal treatment carried out by undergraduate students was effective in the improvement of the periodontal health of patients with moderate and severe chronic periodontitis.