This study aimed to develop a chewing performance scale that classifies chewing from normal to severely impaired and to investigate its validity and reliability. The study included the developmental phase and reported the content, structural, criterion validity, interobserver and intra-observer reliability of the chewing performance scale, which was called the Karaduman Chewing Performance Scale (KCPS). A dysphagia literature review, other questionnaires and clinical experiences were used in the developmental phase. Seven experts assessed the steps for content validity over two Delphi rounds. To test structural, criterion validity, interobserver and intra-observer reliability, two swallowing therapists evaluated chewing videos of 144 children (Group I: 61 healthy children without chewing disorders, mean age of 4238 +/- 936 months; Group II: 83 children with cerebral palsy who have chewing disorders, mean age of 3909 +/- 2295 months) using KCPS. The Behavioral Pediatrics Feeding Assessment Scale (BPFAS) was used for criterion validity. The KCPS steps arranged between 0-4 were found to be necessary. The content validity index was 0885. The KCPS levels were found to be different between groups I and II ((2) = 123286, P < 0001). A moderately strong positive correlation was found between the KCPS and the subscales of the BPFAS (r = 0444-0773, P < 0001). An excellent positive correlation was detected between two swallowing therapists and between two examinations of one swallowing therapist (r = 0962, P < 0001; r = 0990, P < 0001, respectively). The KCPS is a valid, reliable, quick and clinically easy-to-use functional instrument for determining the level of chewing function in children.