In this study, the effect of soluble chitosan, thyme oil and linseed oil on the mold resistance of wood and its surface properties was investigated. Both low and medium molecular weight chitosan with concentration of 1 and 2% were used. Cypress wood samples with dimensions of 20 × 20 × 70 mm and moisture content of 12% were saturated by the preservatives. The results showed that the maximum absorption was for linseed oil and the lowest one for low molecular weight chitosan with concentration of 2%. The lowest and highest leaching values were observed for the samples treated by linseed oil and medium molecular weight chitosan with concentration of 2%, respectively, but these differences do not seem to be statistically different. After 4 weeks, thyme essential oil was able to completely prevent mold growth. Compared to chitosan, linseed oil had a greater inhibitory effect to the growth of mold. Antifungal effect of chitosan was increased by increasing its molecular weight. In contrast to thyme oil and linseed oil, the wood treatment by chitosan increased its wettability. There was no significant difference between the roughness of control and treated samples.