Objective: The aim of the study is to investigate the effects of core strengthening exercises on pain, mobility, and lower limb muscle strength in patients with patellofemoral pain syndrome. Design: Six databases were searched from inception until August 11, 2023. Pain, function, and muscle strength-related outcomes were extracted and the quality of the studies was assessed using the PEDro scale and the level of evidence was assessed using the GRADE. Results: Nineteen studies involving 1138 patients were included. Very low-grade evidence supported the short-term pain-relieving effect of core training (standardized mean difference = −0.60, 95% confidence interval [−0.95, −0.25]), high-grade evidence supported the short-term functional improvement effects of core training (weighted mean difference = 3.61, 95% confidence interval [1.44, 5.78]), which was similarly significant within 3–12 mos of follow-up. The results of the subgroup analyses suggested that hip-knee training was most advantageous in relieving pain and enhancing motor function. Conclusions: Although training that includes trunk core is clearly superior to knee strengthening alone, the effectiveness of hip-knee training, which is also a core training program for pain and function, is more pronounced. The available evidence supports that hip-knee training is the most valuable treatment option for patients with patellofemoral pain syndrome.