The main objective of this study was to evaluate the utilization of alternative protein feed ingredients including sunflower meal (SFM), corn gluten meal (CGM), and dried distillers' grains with solubles (DDGS) as a mixture in a partial replacement of soybean meal (SBM) in broiler finisher diets with different protein levels and also to evaluate their effect on birds' performance, environmental aspects of litter, cecal microbes, and economic prospects. A total of 576 (19 days old) Cobb 500 broiler chicks were fed eight finisher diets consisting of 4 control (CTL) diets based on SBM with different crude protein (CP) levels (CTL21, CTL20, CTL19, and CTL18, containing 21%, 20%, 19%, and 18% CP, respectively) and 4 test diets with alternative protein sources (APS21, APS20, APS19, and APS18, containing 21%, 20%, 19%, and 18% CP, respectively) using a 15% combination of alternative protein sources (2.5% CGM, 5% SFM, and 7.5% DDGS) until 35 days of age. The results indicated that birds fed test diets APS21 and APS20 recorded the highest (P < 0.05) body weight compared to other treatments, but it was not different than the CTL diets fed at these CP levels. The birds fed CTL18 or APS18 recorded the worst feed conversion ratio (FCR) compared to other treatments. Moreover, birds fed test diet containing APS21 recorded better (P < 0.05) European performance efficiency factor and better economic efficiency when compared to other treatments, but it was not different than CTL21. In addition, birds fed diets APS21 and CTL19 showed significantly increased litter Lactobacillus spp. (P < 0.05) compared to other treatments. Cecal Lactobacillus spp. and Escherichia coli (E. coli) were not affected by CTL or APS diets. The counts of cecal Salmonella spp. increased in the CTL21 group compared to other groups. In conclusion, alternative feed ingredients (protein sources) in broiler finisher diets have positive effects in a sustainable way on the productive performance, litter and cecal microbial counts, and improved economic efficiency when compared to CTL diets.