PURPOSE: To investigate the association between choroidal thickness and persistent subretinal fluid (PSF) after surgery for recent-onset rhegmatogenous retinal detachment (RRD). DESIGN: Case-control study. PARTICIPANTS: Fourteen eyes with macula-off RRD (with fovea on and off) that achieved retinal reattachment on funduscopy and demonstrated PSF after surgery (PSF group) were compared with 62 eyes with macula-off RRD (with fovea on and off) that did not demonstrate PSF after surgery (non-PSF group). METHODS: The diagnosis of PSF was made by the detection of subretinal fluid pockets on OCT beyond 6 weeks after surgery. Covariates included baseline demographics, duration of RRD, area of RRD, foveal status, method of subretinal fluid drainage, retinal pigment epithelium (RPE) changes, and choroidal thickness in both eyes. Multivariate regression analysis was performed by adding gender, age, and pathologic myopia into the model. The secondary outcomes included postoperative vision and time to resolution of PSF. MAIN OUTCOME MEASURES: Subfoveal choroidal thickness in affected eyes, measured by enhanced depth imaging OCT images. RESULTS: The percentage of eyes that underwent vitrectomy, scleral buckle surgery, and pneumatic retinopexy were 71.4%, 14.3%, and 14.3% in the PSF group, respectively, and 87.1%, 11.3%, and 1.6% in the non-PSF group, respectively. Eyes with PSF showed significantly thicker subfoveal choroid than eyes without PSF (305±61 μm vs. 200±70 μm, respectively; adjusted difference, 78.6±19.1 μm; 95% confidence interval [CI], 40.3-116.8 μm; P < 0.001). The PSF group demonstrated a greater proportion of RPE changes in fellow eyes (30.8% vs. 1.7%; P = 0.03) and significantly worse best-corrected visual acuity at the 12-month follow-up (P = 0.03). Multiple logistic regression analysis revealed that choroidal thickness of 280 μm or more was a significant factor associated with the presence of PSF (adjusted odds ratio [AOR], 13.4; 95% CI, 3.1-34.7 [P = 0.001]. CONCLUSIONS: Persistent subretinal fluid is associated with increased subfoveal choroidal thickness in surgical and fellow eyes and with RPE changes in the fellow eye. This indicates that PSF likely belongs to the pachychoroid spectrum. In affected eyes, PSF tends to persist for more than 1 year and results in delayed visual recovery.