Abstract: Protein content is a prerequisite for malting quality and it is highly affected by environment. The objective of this study was to quantify the magnitude of genotype by environment interaction and assess the protein content of malt barley genotypes in diversified locations. Eight malt barley genotypes were evaluated in randomized complete block design using three replications at six locations of Tigray, Ethiopia durining 2013/2014 main cropping season. The additive main effect and multiplicative interaction effect model (AMMI) analysis revealed significant differences (p<0.01) for genotype, location and genotype by location interaction for protein content. The magnitude of location was twice the magnitude of genotype. Hence, the malt barley genotypes had not a consistent rank across location. The AMMI model clearly indicated the presence of large magnitude of genotype by location interaction which can be partitioned into four significant interaction principal components. The malt barley genotypes were best explained by the AMMI2. Therefore, this model is vital for protein content study in the area. According to the additive main effect and multiplicative interaction effect biplot 1 analysis and ranking biplot f the GGE the genotypes Holkler and Bekoji were stable for desirable protein content for malting. The AMMI1 biplot indicated that locations Korem, Emba-hasti and Astella were unfavorable having protein content less than the grand mean. However, Hashange Mekhan and Hagara-Selam were favorable with protein content greater than the grand mean. In the malting industry protein content is not the only indicator and other quality requirements have to be incorporated for full packaged recommendation of the malt barley genotypes.