Worldwide, a large quantity of cigarette butts is being released into the environment. The majority of this waste is formed from cellulose acetate (CA) fibers in filters with poor biodegradability and toxic chemicals. This paper presents a solution to recycle CA fibers in mortars. The objective is to characterize the CA and analyse its influence on mortars. Therefore, after characterizing CA fibers, tests are conducted on the fresh state such as slump test. The formulations are prepared based on preliminary workability tests where 0 wt% (standard mortar), 0.2 wt% and 1.3 wt% rates are chosen to replace sand by CA. Mechanical and shrinkage tests are achieved on the hardened mortars. Thermal conductivity and microstructural investigations (SEM, TGA) are performed to understand the previous results.