Mangosteen (Garcinia mangostana L.) is known as the 'Queen of tropical fruits' and comes from the tropical forests of Southeast Asia such as Malaysia. Mangosteen is used for fresh consumption or as a beauty and health supplement. However, difficulties during the harvesting process with limited effective harvesting machines have prevented large scale mangosteen production. This study was conducted to determine the strength of the harvesting force at each stage of the maturity indexes and the appropriate force required for the development of mangosteen harvesting machines. The study samples were classified based on six stages of the indices of mangosteen and mesta varieties. The fruit samples taken at MARDI Sintok, Kedah were subjected to harvesting force, weight, diameter and stalk size. The result shows that the highest yield strength was mangosteen at maturity index 1 with 51.81 N while the lowest was mesta at maturity index 5 with 13.45 N. The study also found that the optimum harvesting force to drop the mangosteen and mesta from a tree was 30.19 N. This study indicated that the higher maturity indexes the lower the harvesting force needed to harvest mangosteen and mesta.