Hydrochar is a solid product of hydrothermal carbonization (HTC) of organic materials. HTC is suitable for converting wet feedstock. Water hyacinth (WH), the aquatic and hence wet plant, is becoming overwhelming in Ethiopia, especially on Lake Tana. The other feedstock, polyethylene terephthalate (PET) pellets waste, is useless and abundant in plastic factories but its higher heating value is better than WH’s, so it is a novel opportunity to use this polymer with the dangerous weed. Therefore, this study focuses on the production of hydrochar from those wastes using a simple and environmentally friendly experimental setup. To elucidate the effects of raw materials ratio, reaction temperature, residence time on the physicochemical properties and combustion behavior of hydrochar, experiments were performed at 140, 210 and 280ºC; for 0.5, 1, and 1.5h with a WH to PET pellets ratio of 1:1, 1:2 and 2:1 followed by product characterization. Results found that an hour treatment at 210 ºC when the WH amount is twice of pellets’ was the optimum condition to enhance the fuel properties of hydrochar in terms of mass yield, higher heating value, fixed carbon percentage, energy density and energy yield. At this condition, the maximum mass loss rate, ignition index, combustion index, burnout index, combustion stability index and combustibility index of the hydrochar were: 39.61wt%/min, 103.04(wt.%/min −3) *10 −3 , 0.8835°C*10 3 , 32.956(wt%/min −4 )*10 −5 , 13.283(min −1 *°C −2 )*10 −5 and 9.17(wt. % / (min −2 *°C −3 ))*10 −7 , respectively. Therefore, the co-HTC of WH and PET pellets can be a promising source of solid fuel. Keywords: Hydrochar, polyethylene terephthalate, water hyacinth, Lake Tana