Up-regulation of heat shock protein 90 (HSP90) gene takes place in lung cancer cells. Therefore, targeting HSP90 in lung cancer may be promising step in lung cancer therapy. The present study aimed to evaluate the efficiency of implantable 17-dimethylaminoethylamino-17-demethoxy geldanamycin (17-DMAG)-loaded Poly(caprolactone)–poly(ethylene glycol) (PCL/PEG) nanofibers to increase the anti-cancer effects via inhibition of HSP90 expression and telomerase activity. For this purpose, 17-DMAG-loaded PCL/PEG nanofibers were successfully fabricated via electrospinning and characterized using FE-SEM and FTIR. Colorimetric MTT assay was used to determine the drug cytotoxicity. Also, the expression levels of HSP90 mRNA in the A549 cells treated with the nanofibers were assessed using Quantitative Real-Time PCR. The effect of free 17-DMAG and 17-DMAG-loaded PCL/PEG nanofiber treatment on telomerase activity was monitored by TRAP assay. MTT assay confirmed that loading of 17-DMAG into PCL/PEG nanofiber enhanced dramatically cytotoxicity in the lung cancer cells. This finding was associated with reduction of HSP90 mRNA expression and telomerase activity in the cells seeded on 17-DMAG-loaded PCL/PEG nanofibers in relative to free 17-DMAG. In conclusion, the findings demonstrated that 17-DMAG-loaded PCL/PEG nanofibers are more effectual than free 17-DMAG against A549 lung cancer cells via modulation of Hsp90 expression and inhibition of telomerase activity. Hence, the implantable 17-DMAG-loaded nanofibrous scaffolds might be an excellent tool for efficiently killing of the lung residual cancer cells and avoid the local cancer recurrence.