Objectives: This systematic review assessed the dentoskeletal effects of Twin Block (TB) and Invisalign clear aligners (CAs) with mandibular advancement features in peripubertal patients compared to Class II non-treated individuals, using lateral cephalography. Materials and Methods: In this modified systematic review, data were collected electronically by searching PubMed Central, Google Scholar, and Cochrane electronic databases. The outcome measures included SNA, SNB, ANB, Wits appraisal, SN^Gn, U1^PP, L1^MP, overbite, and overjet measured at the onset (T1) and at the end (T2) of functional appliance therapy. Results: Nine eligible papers were reviewed: 6 on TB and 4 on CAs (1 study included both appliances). Patients’ mean age ranged from 11.2 to 13.15 years for the intervention groups, and 10.7 to 13.07 years for non-treated controls. An improvement in sagittal intermaxillary relationships was observed, primarily at the mandibular level, when patients were treated at puberty. This was confirmed by an increase in the SNB angle and a corresponding reduction in the ANB angle between the pre- and post-treatment phases, in comparison to non-treated controls, slightly more pronounced with the TB. Mandibular advancement was associated with an increase in mandibular length (CoGn), significantly greater in both treatment modalities compared to non-treated controls. Conclusion: This systematic review showed that both appliances produce significant skeletal effects when applied during the pubertal growth phase, emphasizing mandibular protrusion and skeletal growth. The biological timing of intervention may be a critical factor in understanding the divergent findings reported in the literature.