To protect natural sites from the excessive exploitation of the alluvial sand used in construction fields, many authors investigated the use possibility of the dune sand in concrete and cementitious mortars and showed that this material can be utilized as a fine aggregate or a substitution of the crushed sand. These results were used to develop alluvial-dune sand cementitious mortars which exhibited the best mechanical and physical properties behavior in short time. However, environmental factors' effects on the durability of dune-alluvial sand mortars in long term should be investigated. This paper presents an experimental investigation to formulate alluvial-dune sand mortars (composed from 40% of the alluvial sand and 60% of the dune sand) subjected to temperatures (20 degrees C and 50 degrees C) and magnesium sulfate attacks (10%MgSO4) during 60 days. Results showed that the alluvial-dune sand mortar formulated with and without the superplasticizer exhibits compressive strengths of 39.1 and 28.32 MPa at 28 days, respectively, which are 85% greater than that of the dune sand mortar (MSD) found equal to 15.3 MPa. However, the flexural strengths of the both mortars with and without the superplasticizer were 7.35 MPa and 6.69 MPa at 28 days, respectively. Furthermore, both the dune-alluvial sand mortars with and without the superplasticizer immersed in magnesium sulfate attack at 50 degrees C, exhibited a maximum strength reduction rate of 50% in compressive strength and 54% in flexural strength.