Purpose: Our study aimed to investigate whether CAF (cancer-associated fibroblasts) were involved in long noncoding RNAs (lncRNA)-regulated radioresponse in esophageal squamous cell carcinoma (ESCC). Experimental Design: By use of lncRNAs PCR array, 38 lncRNAs were screened in esophageal cancer cells and in normal esophageal epithelial cells Het-1A. LncRNA DNM3OS was detected in tumor tissues of patients with ESCC and in matched normal esophageal epithelial tissues by qRT-PCR analysis and in situ hybridization assay. The association of DNM3OS and tumor radioresistance was investigated in vitro and in vivo. The influences of DNM3OS on DNA damage response (DDR) was investigated by Western blotting, immunofluorescence imaging, and comet assay. The mechanisms by which CAFs promoted DNM3OS expression was investigated by kinase inhibitors' screening, luciferase assay, and chromatin immunoprecipitation. Results: Among the 38 lncRNAs tested, DNM3OS was found to have a much higher expression level in esophageal cancer cells than in Het-1A. In tumor tissues of 16 patients with ESCC, the expression level of DNM3OS showed an average increase of 6.3429-fold compared with that in matched normal tissues. DNM3OS conferred significant radioresistance in vitro and in vivo by regulating DDR. CAFs promoted the expression of DNM3OS with a 39.2554-fold and 38.3163-fold increase in KYSE-30 and KYSE-140, respectively. CAFs promoted the expression of DNM3OS in a PDGF beta/PDGFR beta/FOXO1 signaling pathway-dependent manner. FOXO1, a transcription factor downstream of PDGF beta/PDGFR beta signaling pathway, initiated the transcription of DNM3OS by binding to DNM3OS promoter. Conclusions: Our study highlighted CAF-promoted DNM3OS as an attractive target to reverse tumor radioresistance in ESCC.