This study was conducted to evaluate the possibility of using alfalfa cubes hay (ACH) as a protein source in the buffalo calves diet for replacing cotton seed meal (CSM) through growth and finishing periods. Twenty male calves weighting 276±9.24Kg were divided into two similar groups (ten calves each) using randomized complete block design. The growing period extended to 85 – d, which the control group (CSM - diet) was fed the concentrate feed mixture (CFM) including CSM as a source of protein and rice straw ad lib. The tested group (ACH - diet) was fed the same diet with replacing CSM by ACH. While, the finishing period lasted for 45 – d, where animals in both groups were fed a high energy diet by adding maize grains. All diets formulated to be an isonitrogenous and isocaloric state. During the growing period, results indicated that the most nutrients digestibilities were significantly (P≤0.05) higher and NFE digestibility was significantly (P≤0.05) lower in ACH - diet. While, there was insignificant difference in EE digestibility between them. While during the finishing period, there were insignificant differences among groups in most nutrients digestibilities, except EE and NFE digestibility were significant (P≤0.05) higher with ACH - diet. During the whole experimental period, growth performance and some blood parameters were insignificantly affected by replacing. Economic efficiency of calves fed ACH – diet was better compared with CSM – diet. It could be concluded that the ACH could be used successfully and economically as a main protein source in the calves' diet.