Purpose. We had earlier reported positive hsa-miR-148a-3p expression in eyes with rhegmatogenous retinal detachment (RRD) and its involvement in the epithelial-mesenchymal transition of retinal pigment epithelium in vitro. Here we investigated the association of hsa-miR-148a-3p expression levels in the vitreous fluid of patients with RRD with severity of RRD. Methods. The hsa-miR-148a-3p expression levels in the vitreous fluid, range (degree) of retinal detachment (RD), and pixels of retinal break were measured in 27 eyes with RRD. The association of hsa-miR-148a-3p expression levels with other factors was evaluated by multiple regression analysis. Results. The hsa-miR-148a-3p expression levels, time from onset of RRD to vitrectomy, range of RD, and pixels of retinal breaks were 23.68 ± 43.00, 12.07 ± 15.36 days, 155.85 ± 86.67 degrees, and 37000 ± 67100 pixels, respectively. Five eyes with RRD had vitreous hemorrhage preoperatively. The hsa-miR-148a-3p expression levels were significantly associated with pixels of retinal breaks (β = 0.699) and the time from onset of RRD to vitrectomy (β = 0.358) but not with the range of RD or presence of vitreous hemorrhage. Conclusion. The hsa-miR-148a-3p expression levels in the vitreous fluid were significantly associated with the size of retinal break and disease duration.