A combination of a metal coagulant with an organic polymer can complement both the outstanding and flaw properties of the separate elements. A novel composite coagulant of polyaluminium chloride (PAC)-tapioca peel extract powder (TPP) called PACTPP with different weights ratio was prepared in this study. In the preliminary study, PACTPPg at the weight/weight ratio of TPP/Al=3.71 was selected as the optimum one based on the performance in treating wastewater sample of landfill leachate. Through all characterisation analyses, it revealed that the novel composite reagent exhibits better coagulant properties when compared with the individual coagulants of PAC and TPP. It was characterised that PACTPPg had combined the best benefits from PAC and TPP, with an acidic property of pH 3.45, the low charge density of 3.45 mV, the higher molecular weight of 1.59 × 107 g/mol, the bigger particle size of 4.528 × 104 d.mn, and a longer connected and compact structure. Through Fourier transform infrared (FTIR) and X-ray diffraction (XRD) analyses, PACTPPg was identified to comprise new chemical compounds, i.e., the functional groups of ketones, aldehydes, and alkanes in a semi-formed crystalline phase. Based on the comparison study, it can be concluded that PACTPPg showed a correlation to encompass the complex interpenetration networks rather than just a simple mechanical mixing of raw materials.