BACKGROUND Balance weaknesses related to mobility and fall risk in patients with rheumatic diseases are well-known. Vestibular dysfunction could negatively contribute to the balance ability of this patient population. This study aims to investigate the effects of Rheumatoid Arthritis (RA) and Ankylosing Spondylitis (AS), among the most common rheumatic diseases, on postural balance related to vestibular function. METHODS Seventy-eight participants were grouped as RA (n=34, 43%), AS (n=24, 30.7%), and the control group consisted of healthy individuals (n=20, 25.6%). Cervical Vestibular Evoked Myogenic Potentials (cVEMP) test, which assesses the vestibular function objectively, Dizziness Handicap Inventory (DHI), which evaluates vertigo subjectively, and Berg Balance Scale (BBS) were performed. RESULTS Different degrees of VEMP latency prolongations were found in the AS and RA groups. Right, and left ear N1 latencies were significantly longer in the AS group than in RA and control. Right ear P1 latency prolongation was statistically significant in the RA group. Amplitude asymmetry ratio (AAR) was found to be considerably higher in the RA and AS groups than in the control group (p<0.05). The mean BBS score in the AS group was below the fall risk score of 45. A negative statistically significant effect was observed between latency prolongation and BBS in AS groups. CONCLUSIONS The abnormal VEMP findings in individuals with RA and AS shows inner ear vestibular system dysfunction. This vestibular impairment strictly contributes to their postural imbalance and requires a focused vestibular rehabilitation program for balance treatment.