Background <p>Tongue reconstruction after oncologic resection aims to restore critical functions such as swallowing and speech. The radial forearm free flap (RFFF) and anterolateral thigh flap (ALT) are widely used techniques, though comparative evidence remains heterogeneous. We aimed to synthesize comparative evidence between ALT and RFFF in oncologic tongue reconstruction, focusing on functional outcomes, flap success, and donor-site morbidity.</p> Methods <p>A systematic review (PRISMA) of observational comparative studies was conducted using PubMed, Embase, and LILACS up to February 2026. Nine comparative observational studies were included. Five studies provided direct comparative functional data in 198 patients, while four studies contributed complementary evidence on volumetric changes, donor-site morbidity, perioperative outcomes, and patient-reported measures. A structured narrative synthesis was performed without meta-analysis, and methodological quality was assessed using the Newcastle–Ottawa Scale.</p> Results <p>Flap survival was near 100% in most studies (e.g., 97.8% vs. 97.4%; <i>p</i> = 1.000). No significant differences were found in swallowing, speech, or quality of life across most comparisons (<i>p</i> &gt; 0.05). ALT demonstrated lower volumetric contraction (39.6% ± 3.9% vs. 51.1% ± 6.2%; <i>p</i> = 0.008) and reduced donor-site morbidity (0% vs. up to 9.5%; <i>p</i> = 0.035). RFFF showed better tongue mobility in one study (<i>p</i> = 0.045) and shorter operative time.</p> Conclusions <p>Both flaps provide comparable functional outcomes. ALT offers advantages in donor-site morbidity and volume preservation, whereas RFFF is preferable in defects requiring thinner and more flexible tissue.</p> <p>Level of Evidence: Not gradable.</p>