For adolescent people with ID, falls are more common compared to peers without ID. However, postural balance among this group is not thoroughly investigated. The aim of this study was to compare balance and muscle performance among adolescents aged between 16 and 20 years with a mild to moderate intellectual disability (ID) to age-matched adolescents without ID. A secondary purpose was to investigate the influence of vision, strength, height and Body Mass Index (BMI) on balance. A group of 100 adolescents with ID and a control group of 155 adolescents without ID were investigated with five balance tests and three strength tests: timed up and go test, one leg stance, dynamic one leg stance, modified functional reach test, force platform test, counter movement jump, sit-ups, and Biering-Sørensen trunk extensor endurance test. The results showed that adolescents with an ID in general had significantly lower scores in the balance and muscle performance tests. The group with ID did not have a more visually dominated postural control compared to the group without ID. Height, BMI or muscle performance had no strong correlations with balance performance. It appears as if measures to improve balance and strength are required already at a young age for people with an ID.