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We propose and demonstrate a cost-effective and facile electrochemical procedure to detach films with (In,Ga)N nanowires from the original Si substrate used for growth. Without ultraviolet illumination and mechanical force, this lift-off process can be completed quickly within a few seconds. The key element for the underlying mechanism is a thin AlN layer, which acts both as a buffer layer in the epitaxial process and as a sacrificial layer in the etching process. Taking advantage of the high etching selectivity of AlN over GaN, the AlN layer can be etched quickly whereas only few reactants remain on the GaN NWs, and the latter do not suffer from corrosion. Based on this lift-off procedure, a film comprising a dense ensemble of (In,Ga)N nanowires with good flexibility and transmittance can be obtained easily. We show both light emission and mechanical–electrical energy conversion for such detached films, hence substantiating perspectives for future applications. Therefore, this lift-off method for GaN-based nanowire films is promising for mass production and various devices requiring high flexibility and/or high transmittance, including wearable intelligent electronics and piezoelectric devices.