Generation of waste foundry sand as by-product of metal casting industries causes environmental problems because of its improper disposal. Thus, its usage in building material, construction and in other fields is essential for reduction of environmental problems. Similarly, in foundries (where the ferrous and non-ferrous metals are melted.), the slag is produced after the completion of the melting process it can also be used as a building material, construction and in other fields. This research is carried out to produce low-cost and eco-friendly concrete. This paper demonstrates the use of waste foundry sand as a partial replacement by fine aggregate and slag is as coarse aggregate in concrete. An experimental investigation is carried out on concrete containing waste foundry sand in the range of 0%, 20 %, 40% by weight and slag is fully replaced (100%) for M-25 grade concrete (OPC). The material was produced, tested and compared with conventional concrete in terms of workability and strength. These tests were carried on a standard cube of size 150mm×150mm×150mm for 7, 14 and 28 days to determine the mechanical properties of concrete.