We present details of the construction of a wideband, cryogenic receiver and its successful commissioning on the Arecibo 12m telescope. The cryogenic receiver works in the 2.5-14 GHz frequency range. The receiver is built around a Quadruple-Ridged Flared Horn (QRFH) developed by Akgiray et al. (2013)[2]. To mitigate strong radio frequency interference below 2.7 GHz, we installed a high-pass filter before the first stage low noise amplifier (LNA). The QRFH, high-pass filter, noise coupler and LNA are located inside a cryostat and are cooled to 15 K. The measured receiver temperature is 25 K (median value) over 2.5 to 14 GHz. The system temperature measured at zenith is about 40 K near 3.1 and 8.6 GHz and the zenith antenna gains are 0.025 and 0.018 K/Jy at the two frequencies respectively.