This paper presents a CMOS RF-to-DC converter with a cross-coupled charge pump for energy harvesting. The proposed RF-to-DC converter consists of a cross-coupled rectifier and a cross-coupled charge pump. The charge pump can operate with a non-overlapping clock with a switching frequency of 25 MHz using a pump capacitance of 4 pF. The RF-to-DC converter IC was designed and fabricated using a 0.13 μm CMOS process. An output voltage of 2.05 V was achieved at an RF input power of -6 dBm with an input frequency of 900 MHz and the load of 100 KΩ. For this condition, the charge pump exhibited a high efficiency of about 74 %.