Manufactured sand is a term used for aggregate materials less than 4.75mm and which are processed from crushed rock or gravel. Due to the booming of construction activities in our country, natural sand resources are increasingly depleted and its cost is becoming increasingly high. This research was, therefore, conducted to study the Effects of Using Natural Sand and Manufactured Sand for The Production Of C-25 Concrete and to assess the prospects of using manufactured sand as a replacement of natural sand in Ethiopia. Initially, different natural and manufactured sand samples to be used in the concrete mixes were collected and their physical properties were studied. Fifteen different concrete mixes having five mix proportions for both natural and manufactured sand (i.e. 100%NS+ 0%MS; 75%NS+25%MS; 50%NS+50%MS; 25%NS+75%MS and 0%Ns+100%MS) were prepared for C-25 Concrete strength using EBCS mix design procedure. The properties of these mixes have then been assessed both at the fresh and hardened state. The using of manufactured sand as a fine aggregate has a significant effect on the workability and finishing ability of the concrete, also, the results of hardened properties of the mixes have shown that concrete mixes with partial proportions of manufactured and natural sand achieved a higher compressive strength at all test ages. The result also has shown that using manufactured sand in partial or full replacement to natural sand doesn’t cause any significant effect on the compressive strength of concrete. It has been found also that the use of manufactured sand is more suitable for high strength concrete production. It can, therefore, be concluded from the findings of this research that when the availability of natural sand is scarce or in cities where the price of natural sand is as expensive as manufactured one, manufactured sand concrete mix is a viable and better alternative to the use of natural sand.