Background: This study examined the impact of age-adjusted cerebrospinal fluid (CSF) protein levels on clinical characteristics, disease severity, and outcomes in Guillain–Barré Syndrome (GBS) patients. Methods: This retrospective study included 71 GBS patients at UTMB Galveston. Albuminocytologic dissociation (ACD) was defined as CSF–total protein (CSF-TP) >0.45 g/L with a cell count of 0.45 g/L) and age-adjusted upper limits (URLs) for CSF-TP levels, comparing clinical, CSF, and electrophysiological characteristics across groups. Results: The mean age was 50 years (SD = 14.5). The mean age of patients with a CSF-TP > 45 g/L was higher (53 vs. 39 years, p = 0.000), whereas no such difference was noted using age-dependent URLs. Using age-adjusted CSF-TP URLs reduced the sensitivity for detecting ACD by 20%. CSF-TP > age-adjusted URLs were associated with lower MRC sum scores (39 vs. 47.43, p = 0.000), higher ICU admission rates (34% vs. 20%, p = 0.003), and the need for second-line treatment (41% vs. 17%, p = 0.049), and the trends were not observed with the conventional cutoff of 0.45 g/L. CSF-TP was an independent predictor of lower MRC sum scores (p = 0.009, 95% CI −0.058, −0.009) and higher GBS disability scores (p = 0.015, 95% CI 0.000, 0.004). Conclusions: ACD is a common finding in GBS, but normal protein levels do not exclude the diagnosis. Using age-adjusted URLs might improve specificity but reduce sensitivity for ACD detection, potentially increasing false negatives. CSF-TP levels exceeding age-adjusted URLs were more strongly associated with greater disease severity and poorer outcomes compared to the conventional cutoff of 0.45 g/L.