In this paper, we report a cost effective and facile approach to produce uniform nanostructural black silicon over large-area by metal assist chemical etching followed by its transfer over pressure sensitive flexible substrate. Structural and optical properties of black silicon over flexible substrate were investigated. Field emission scanning electronic microscope (FESEM) reveals textured surface and dense morphology of silicon nanostructures; that appeared to be black. An intense and broadband UV and Visible photoluminescence spectra from these nanostructures was observed and suggested the optically active nature of black silicon. Broadening and asymmetric shifting of Raman line shape, corresponding to black silicon, confirmed quantum confinement of phonon. The crystal sizes of silicon (Si) nanostructures calculated using frequency shift in Raman spectra analytical model were 3.4 nm to 4.7 nm. Significant reduction of reflection below (1%) over the wide UV–Vis spectrum was recorded due to presence of textured surface as observed by FESEM. The present work aids our understanding of tuning the optical properties of black silicon and its’ realization on flexible substrate could be beneficial for flexible electronics including bio-sensing and optoelectronics devices. More interestingly low reflectance of black silicon could pave the way for realization of highly efficient flexible solar cells. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.