Objective The risk factors for residual dizziness (RD) after successful treatment of benign paroxysmal positional vertigo (BPPV) are poorly characterized. We determined the risk factors for RD in patients with benign unilateral posterior semicircular canal paroxysmal positional vertigo (pc-BPPV) after successful treatment. Methods We conducted a prospective study of patients diagnosed with unilateral pc-BPPV between March 2015 and January 2017. Bone mineral density (BMD) was measured by dual-energy X-ray bone mineral densitometry. Participants underwent bithermal caloric testing (C-test) using videonystagmography and a canalith repositioning procedure (CRP). The occurrence of RD was the primary outcome. The participants underwent follow-up 1 week, 1 month, and 1 year after successful CRP, consisting of outpatient visits, questionnaires, and telephone interviews. Results We assessed 115 participants with unilateral pc-BPPV (31 men and 84 women) who were 53.2 ± 8.8 years old. RD occurred in 60 (52.2%) participants. The participants who experienced RD were older, had vertigo for longer before treatment, and were more likely to show a positive C-test and significant BMD loss. Conclusions We found that a significant reduction in BMD (T-score  < −1 standard deviation), a positive C-test, and older age are independently associated with RD in patients with pc-BPPV after successful CRP.