Borderline personality disorder (BPD) is a psychiatric condition characterized by severe instability in affect, impulse control, and interpersonal functioning. Existing literature has confirmed that BPD is highly comorbid with other psychiatric conditions, including anxiety disorders. Despite this, little research has investigated the nature of the relationship between generalized anxiety disorder (GAD) and BPD. The aim of this systematic review and meta-analysis is to synthesize the literature concerning the prevalence and clinical outcomes of BPD and GAD comorbidity in adults. The following three databases were searched on October 27, 2021: PsycINFO, PubMed, and Embase. Twenty-four studies were included (n = 21 reporting on prevalence of the comorbidity, n = 4 reporting on clinical outcomes associated with the comorbidity), 9 of which were included in a meta-analysis. The meta-analysis showed that the pooled prevalence for current GAD in individuals with BPD was 16.4% (CI 95%: 1.9%; 66.1%) in inpatient samples, and 30.6% (CI 95%: 21.9%; 41.1%) in outpatient or community samples. The pooled lifetime prevalence of GAD in individuals with BPD was 11.3% (CI 95%: 8.9%; 14.3%) in inpatient samples, and 13.7% (CI 95%: 3.4%; 41.4%) in outpatient or community samples. Comorbidity between BPD and GAD was associated with worse outcomes on measures of BPD severity, impulsivity, anger, and hopelessness. In conclusion, this systematic review and meta-analysis indicate that comorbid GAD and BPD is highly prevalent, although the pooled prevalence rates should be interpreted with caution considering the large and overlapping confidence intervals. Further, this comorbidity is associated with worse BPD symptom severity.