The purpose was to perform a systematic review of clinical assessment methods for classifying Generalized Joint Hypermobility (GJH), evaluate their clinimetric properties, and perform the best evidence synthesis of these methods. Four test assessment methods (Beighton Score [BS], Carter and Wilkinson, Hospital del Mar, Rotes‐Querol) and two questionnaire assessment methods (Five‐part questionnaire [5PQ], Beighton Score‐self reported [BS‐self]) were identified on children or adults. Using the Consensus‐based Standards for selection of health Measurement Instrument (COSMIN) checklist for evaluating the methodological quality of the identified studies, all included studies were rated “fair” or “poor.” Most studies were using BS, and for BS the reliability most of the studies showed limited positive to conflicting evidence, with some shortcomings on studies for the validity. The three other test assessment methods lack satisfactory information on both reliability and validity. For the questionnaire assessment methods, 5PQ was the most frequently used, and reliability showed conflicting evidence, while the validity had limited positive to conflicting evidence compared with test assessment methods. For BS‐self, the validity showed unknown evidence compared with test assessment methods. In conclusion, following recommended uniformity of testing procedures, the recommendation for clinical use in adults is BS with cut‐point of 5 of 9 including historical information, while in children it is BS with cut‐point of at least 6 of 9. However, more studies are needed to conclude on the validity properties of these assessment methods, and before evidence‐based recommendations can be made for clinical use on the “best” assessment method for classifying GJH.