Background and objectives: Soft denture liners act as a cushion for denture-bearing mucosa through absorption and redistribution of the masticatory forces. The most common problem encountered using soft denture liners is lack of interfacial bond strength. The objective of this study was to evaluate and compare the effect of surface pretreatments by the methyl methacrylate monomer on shear bond strengths of two silicone-based soft liners. Materials and methods: A total of 240 heat-polymerized acrylic resin blocks of dimension 30 mm × 10 mm × 10 mm, were fabricated using stainless steel die. Each sample consisted of two resin blocks with the liner embedded in-between them. The study was divided in two different groups that were lined with Mollosil and Sofreliner Tough M. Each having two different subgroups: No surface treatment and surface treatment with methyl methacrylate monomer wetting. After surface treatment, the adjacent two blocks were joined with their respective reliners. After 24 hours storage, all specimens were placed under shear stress until failure occurred. The shear bond strength values obtained were tabulated and analyzed for statistical significance using ANOVA and the Tukey's Honesty significance difference (HSD) test. Results: The results of the study revealed when no surface treatment was done, Mollosil showed mean shear bond strength of 0.5507 MPa and Sofreliner Tough M showed 1.6020 MPa. When monomer wetting was done, Mollosil showed a mean shear bond strength of 0.6200 MPa and Sofreliner Tough M showed 1.8073 MPa. Irrespective of the surface treatment, Sofreliner Tough M showed the higher shear bond strength. There was statistical significance (p < 0.001) between all groups when subjected to surface treatments. Interpretation and conclusion: Within the limitations of this in vitro study, surface treatment with methyl methacrylate monomer enhanced the shear bond strength significantly in both groups and group II, Sofreliner Tough M, showed the higher shear bond strength.