Heat treated pine samples at a temperature of 220 \({}^{\circ}\)C also had 2.7% and 1.95% reduction in their tangential and radial grain orientation swelling, respectively [11]. Discoloration in the form of being darker is also one of the results of heat treatment of wood. Naturally, this characteristic is more prominent in the case of light color species such as pine or yellow poplar [18]. Degradation of hemicelluloses and extractive content in wood are main parameters influencing discoloration of the member during heat treatment process [21; 22]. In a past study yellow poplar, eastern redcedar and southern pine samples exposed to temperature levels of 130 \({}^{\circ}\)C, 160 \({}^{\circ}\)C, and 190 \({}^{\circ}\)C had average lightness values ranging from 32.82 to 68.75 [18]. Most of the experimental heat treatment processes of wood and wood products are carried out using a laboratory type oven. Although dry-klin type compartments are effectively used for a commercial scale operation but heat treatment process is quite time consuming in both approaches. Microwave heat treatment is relatively new approach and has been getting a certain attention in heat treatment of wood products. Better temperature control and more homogeneous distribution of heat within the sample in a short time would be considered some of the main advantages of this technique. This technology provides substantial energy, material and time saving as compared to traditional heat treatment methods [23; 24; 25]. It is expected that microwave heat treatment of wood products will be getting more popular for lumber and other products including particles and biomass. Rubberwood (_Hevea brasiliensis_) is an indigenous species to Amazon forestland in Brazil. Around 1840 this species was introduced to South East Asian countries including Malaysia, Thailand, and Vietnam [26]. Rubber tree is tapped to produce natural latex until age of 20-25 years old during its productive life span. Until several decades ago majority of rubber trees were wasted by burning or land filling once tree reached its unproductive life. However, rubberwood is highly demanded and used for mainly furniture production, plywood and veneer manufacture as well as a raw material for value-added composite panels such as particleboard or fiberboard production [26; 27]. Thailand is a major exporter of rubberwood in South East Asia. An approximate rate of 65% rubberwood products of the country is shipped aboard. It is expected that such value will be increasing linearly within next two decades. Both mechanical properties of rubberwood are slightly lower than those of typical oak with an exception of dimensional stability. During the heat treatment of wood, density, anatomical structure and units size are some of the parameters influencing overall quality of the process. Application of microwave heat treatment would be ideal for species having less permeability such as oak or map. It is clear that low permeable species will simply resist heat transfer during the treatment resulting in longer processing time. This would also create certain amount of excessive discoloration on the samples especially when higher temperature levels are used. In the case of rubberwood being as relatively porous hardwood species used in this work, reducing heat exposure time in a microwave would be considered as a main advantage. Such advantage will not only create overall lower energy consumption but also complete the process within a short period of time without having any possible defects. Most of the properties of the rubberwood have been evaluated and tested in previous investigations [26; 27]. However, there is very limited information on behavior of microwave heat treated rubberwood. Therefore, the main objective of this study was to evaluate both physical and mechanical properties of heat treated rubberwood samples in a microwave oven. Bending properties, hardness, anatomical change, and dimensional stability of such samples were also determined within the scope of the study.