The purpose of this study is to evaluate the effect of polymers on the tensile adhesion strength of cementitious tile adhesives in relation to their formulation. In Ethiopian modern construction, ceramic tile, terrace, and mosaic, which are used for finishing and decoration, are attached to the surface by using polymer -modified cementitious tile adhesives. This thesis examines the influence of polymers on the tensile adhesion strength of cementitious tile adhesives. In this research, tensile adhesion strengths in different conditio ns (initial time, open time, extended open time, water immersion, and heat cycle) were determined. Two types of cellulose ethers (modified and non-modified cellulose ethers) and two types of redispersible polymers (Ethylene and vinyl acetate base polymer (EVA) and Vinyl Esters, ethylene, and acrylic acid esters base polymer (EVEA)) have been compared and tested in terms of slip resistance and adhesion strength. The modified cellulose ether is better than the non-modified cellulose ether. In addition, the modified cellulose ether is better in tensile adhesion strength in all different conditions except extended open time. In terms of tensile adhesion strength, EVA is better than EVEA in all test conditions. The highest tensile adhesion strength that fulfills C1TE (normal setting cementitious adhesive with reduced slip and extended open time) and C2TE (improved setting cementitious adhesive with reduced slip and extended open time) in all conditions is achieved at 35% cement content,1% of polymer content and 0.5% of cellulose and at 40% cement content,2% of polymer content and 0.4% of cellulose ether respectively. The highest tensile adhesion strength that fulfills C1T (normal setting cementitious adhesive with reduced slip) and C2T (improved cementitious adhesive with reduced slip) in all conditions is achieved at 30% cement content, 1.5% of polymer content, and 0.5 % of cellulose, and at 40% cement content,2% of polymer content and 0.4% of cellulose ether respectively. KEY WORDS: Cellulose ether, re-dispersible polymer, tensile adhesion strength, cementitious tile adhesive, slip resistance