<p>Visible light communication (VLC) systems have recently gained significant attention; this green technology provides a broad spectrum and minimal interference, making it a promising alternative in next-generation communications where higher data rates are needed. The modulation type is a very influential part of the communication system that supports these data rates. Orthogonal frequency division multiplexing (OFDM) is one of the most considerable modulations in the VLC, where it can provide high data rates while facing issues with poor spectral efficiency, high peak-to-average power ratio (PAPR), and out-of-band (OOB) emissions. Despite its relatively high complexity, GFDM (generalized frequency division multiplexing) modulation is an exciting solution that provides high data rates and solves OFDM issues. This paper, for the first time, presents a DCO-GFDM (DC-biased GFDM) technique using discrete cosine transform (DCT) for VLC systems, which requires real and positive input to its optical source. DCT-DCO-GFDM fulfilled to reduce the computational complexity associated with modulation and demodulation. It eliminates the need to rely on Hermitian symmetry (HS), which doubles the number of subcarriers needed to convert complex symbols into real ones in a system that uses the fast Fourier transform (FFT). Simulation results show that the proposed DCT-based DCO-GFDM scheme achieves close performance of bit error rate (BER) relative to the conventional FFT-based DCO-GFDM while offering significant complexity reductions and doubling spectral efficiency. This complexity reduction leads to more efficient processing, lower response time, and improved overall system performance. Consequently, this proposed technique can enhance the efficiency of the VLC system, making it a promising candidate for future optical wireless communication technologies.</p>