The Big Five personality traits (i.e., neuroticism, conscientiousness, extraversion, agreeableness, and openness) are indicative of an individual’s enduring behavioural and psychological tendencies across their lifespan. Personality traits are linked to several biological outcomes, particularly for older adults. An emerging body of research suggests that personality traits may be related to allostatic load in older adulthood. Allostatic load is an index reflecting physiological dysregulation based on multiple biological systems. Although operational definitions vary between studies, indices of allostatic load typically includes a range of biomarkers that are standardized and averaged, where higher values indicate higher levels of physiological dysregulation. Across the existing research, biomarkers contributing to allostatic load indices have included measures of cardiovascular functioning (e.g., systolic and diastolic blood pressure), metabolic functioning (e.g., hemoglobin, cholesterol, waist circumference), and inflammation markers (e.g., C-reactive protein, erythrocyte sedimentation rate, procalcitonin). However, findings regarding the association between personality traits and allostatic load are relatively inconsistent, which may be due to heterogeneity in operational definitions of allostatic load across studies. This systematic review aims to synthesize and critically analyze the outcomes of the existing literature reporting the association between the Big Five personality traits and allostatic to assist in identifying which (if any) study characteristics may be contributing to inconsistencies in the field.