Otosyphilis is a serious complication of syphilis. 329 participants enrolled in a study of cerebrospinal fluid (CSF) abnormalities in syphilis underwent portable audiometry (250 Hz to 8000 Hz at 5–75 dB); it was repeated in 33 after otosyphilis treatment. Treponema pallidum spp pallidum ( T. pallidum) DNA in blood was quantitated by polymerase chain reaction. Odds ratios (ORs) or hazard ratios (HRs) with 95% confidence intervals (CIs) were determined by logistic, ordinal or Cox regression. 166 (50.5%) had normal hearing; 15 (4.6%) had low frequency (LF) loss alone, 93 (28.3%) had high frequency (HF) loss alone, and 55 (16.7%) had both. Adjusted odds of any hearing loss were higher with detectable blood T. pallidum DNA (3.00 [1.58–5.69], p = 0.001), CSF pleocytosis (2.02 [1.12–3.66], p = 0.02), and older age (2.22 per 10-year increase, [1.70–2.91], p < 0.001). HRs of normalization of LF and HF loss were lower for older individuals (0.20 [0.07–0.63, p = 0.005] and 0.22 [0.05–0.94, p = 0.04]), and HRs for normalization of HF loss were lower for those with more severe loss (0.09 [0.02–0.43], p = 0.002), and in those with CSF pleocytosis (0.32 [0.11–0.96], p = 0.04). Older age and CSF pleocytosis increase the likelihood of otosyphilis and impair hearing recovery after otosyphilis treatment.