This study was done to evaluate different fiber placement methods on fracture resistance and microleakage of MOD cavities on a molar teeth. The study was carried out in two parts, the fracture resistance test group (T1) and the microleakage test group (T2). 110 third molars were randomized (T1:n1/4=80, T2:n1/3=30). MOD cavities restored after being prepared as standard were as follows: group K; composite restoration (Gaenial Posterior, GC), group KFT; cavity lined with polyethylene fiber (Ribbond, Ribbond Inc. Seattle, WA, USA) + composite restoration, group KFH; polyethylene fiber circumferentially placed on the inner walls of the cavity + composite restoration. Group Control for T1 were intact teeth. The microleakage values, fracture strength, and fracture types were evaluated. Statistical analysis was performed with Kruskal Wallis H and MannWitneyU tests. It was found that fracture strength were not significantly different between the groups (p> 0.05). Groups KFT and KFH had more restorable fracture types than Group K. Group KFT and KFH microleakage values were significantly lower than Group K (p<0.05), but there was no difference between each other (p> 0.05). As a result of these findings, it is seen that the use of polyethylene fiber in the restoration of MOD cavities provides an advantage to composite restorations.