Introduction: Chronic low back pain (CLBP) is a multifactorial entity encompassing a biopsychosocial model. Changes in pain mechanisms have been reported in adult populations as an increase in peripheral and central sensitization. Muscle hypertonicity is present in other chronic pain conditions, however it is unknown to what extent it plays a role in CLBP. Pain catastrophizing (PC) is a comorbidity to CLBP. Most of the literature regarding pain mechanisms in CLBP patients is directed towards adults. There is a lack of knowledge regarding pain mechanisms, muscle tone and PC in adolescents with CLBP. Method: 33 females between 15-19 years (CLBP n = 22) participated. Handheld pressure algometry and computerized pressure algometry (CPA) was used to investigate the presence of local and widespread hyperalgesia. CPA was used to investigate temporal summation (TS) and conditioned pain modulation (CPA). A myotonometer was used to investigate muscle tone. The Pain Catastrophizing Scale (PCS) was used to control for the impact of psychosocial factors on pain. Results: The CLBP group has lower pressure pain thresholds (PPT) compared with the control group. There was significantly higher muscle tone in the left m. gluteus medius in the CLBP group compared with the control group. TS and CPM was present in both the CLBP group and the control group, but there was no significant difference between the two groups. PC scores were significantly higher in the CLBP group than in the control group. There was no significant correlation between PC and TS and CPM. Conclusion: Adolescent females with CLBP share some of the pain mechanisms seen in adults in terms of peripheral sensitisation and widespread hyperalgesia; however, there is a need for further research regarding the impact that PC may have on the development of TS and CPM. It appears that muscle hypertonicity in the left gluteus medius muscle could be a risk factor for developing CLBP and further studies should investigate this relationship.