The purpose of this study is to evaluate hearing outcomes following partial stapedectomy according to age at the time of surgery and evaluate functional hearing at ≥ 10 years' follow-up, and to assess the effect of delay in surgery on overall functional hearing outcomes. Data were collected from patients operated upon for otosclerosis by a single surgeon from 1990 to 1999. Pure-tone air (PTA), pure-tone bone (PTB), air-bone gap (ABG), air-conduction at 8 kHz (AC 8), bone-conduction at 4 kHz (BC4) and speech discrimination score (SDS) were compared between patients <45 and ≥ 45 years old, as well as correlated with overall age preoperatively, short term (4 months) and long term (>10 years), postoperatively. Forty-five patients were included with a mean follow-up of 12.6 years. Mean preoperative ABG and AC 8 values were significantly different between the two age groups (p = 0.002; p = 0.010, respectively). No values remained significantly different between the two age groups at the long-term follow-up. ABG values correlated with age preoperatively (p = 0.001), although no correlation was seen short- and long-term postoperatively (p = 0.980; p = 0.495, respectively). Mean PTA, PTB, and ABG values showed a significant improvement in both groups preoperatively to short-term postoperatively (p < 0.001). Although mean PTA values decreased significantly from short- to long-term follow-ups in both groups (p = 0.033; p = 0.020), the improvement from the preoperative state remained significant (p < 0.001). Regardless of age at the time of surgery, long-term hearing levels will evolve similarly in patients <45 and ≥ 45 years old. Furthermore, no difference will be seen in hearing measurements between the two age groups at ≥ 10 years postoperatively. Delaying a surgery would thus not affect overall long-term hearing outcomes.