Mangosteen prices are determined by traders who tend to speculate, causing a weak bargaining position for farmers. Prices are determined unilaterally by traders, making farmers position only as price takers. Mangosteen marketing efficiency analysis needs to be done so that it can discover the cause of the low bargaining power of farmers and price fluctuations and the level of efficiency in each marketing channel. The study aims to analyze the marketing functions, costs, and the marketing efficiency of mangosteen fruit in Pulau Rambai Village, Kampa District, Kampar Regency. The method used is a survey method. Farmer sampling in this study used a simple random sampling method, and as for the traders, samples were taken by census method. The data analysis used is descriptive and quantitative. The results of the study highlight that the marketing functions carried out by each marketing institution are the exchange function, physical function, and facility functions. The exchange function is carried out in the form of a sale and purchase function. Physical functions is performed in the form of packaging, transportation and storage functions. The function of the facilities carried out in the forms of the activities of sorting and grading, financing, risk management, and market information. There are two mangosteen marketing channels in Desa Rambai Island. The most efficient marketing channels are determinedby thecalculation of marketing costs and marketing efficiency. The most efficient chaanel in this study is marketing channel number two.