The objective of this research was to collect data on the prevalence of phenylketonuria in Jordan, to assess the nutritional status and physical growth of a sample of PKU patients in Jordan using anthropometric measurements and evaluation of the adequacy of their diets. Twenty five patients were divided, according to their age, into four groups: 4–6 months age (n = 6), 8–12 months age (n = 5), 2 years old (n = 7) and 4 years old (n = 7). Height, weight, triceps and subscapular skinfold thicknesses were measured. Dietary intake was taken using three-day food records, and blood phenylalanine (Phe) concentration was determined. The results indicated that 48% of the whole sample had poor physical growth; about (66%) of patients in group 1, (40%) of patients in group 2, (28%) of patients in group 3 and (57%) of patients in group 4 were underweight. Significant positive correlations (p < 0.05) were found between protein intake and each of head circumference (r = 0.434) weight (0.420) and height (r = 0.502) of patients. The protein intakes were 77% and 88% of the recommended levels for groups 1 and 2 respectively. Other low dietary intakes included energy (in groups 1 and 4), fat (in groups 1 and 3) and selenium (in group 1). All patients had controlled blood Phe levels except those in group 4 (4 years age) who had a concentration of 358 µmol/L. It is concluded that there is need for counseling the community about the relationship between PKU and consanguineous marriages and for stressing the importance of monitoring the dietary management of PKU patients.