The aim of this research was the visual characterization and investigating the effects of Alternaria spp. contaminated wheat grains in the starter stage of broilers nutrition on productive parameters and oxidative stress. The research was divided into two phases. Bunches of wheat in post-harvest period of year 2020 was collected from a various locality in Serbia and Albania. In the first phase, collected samples were visual characterized by Alternaria spp. presence by color measurement methods. Gained results are conferred in the range of the color properties of grain color properties of Alternaria toxins. Wheat grain samples were significantly different (p < 0.05) in terms of all measured color parameters (L*, a*, b*). Classification of field fungi in analyzed wheat grain samples showed that the significant field fungi were Rhizopus spp., followed by Alternaria spp., and Fusarium spp. In the second phase, biological tests with chickens were carried out during the broiler chickens’ dietary starter period in the first 14th days of age. At the beginning of the experiment, a total of 180-day-old Ross 308 strain broilers were equally distributed into three dietary treatments, with four replicates each. Dietary treatments in the experiments were as follows: basal diet without visual contamination of Alternaria spp. with 25% wheat (A1), a basal diet with visual contamination of Alternaria spp. with 25% wheat from Serbia (A2), basal diet with visual contamination of Alternaria spp. with 25% wheat from Albania (A3). The trial with chickens lasted for 14 days. After the first experimental week, wheat infected with Alternaria spp. in treatment A2 and A3 expressed adverse effects. The highest body weight of chickens of 140.40 g was recorded in broilers on control treatment A1 with statistically significant differences (p < 0.05) compared to treatments A2 (137.32 g) and A3 (135.35 g). At the end of the second week of test period, a statistically significant (p < 0.05) difference in body weight of broiler chickens could be noticed. The highest body weight of 352.68 g was recorded in control treatment A1, with statistically significant differences compared to other Alternaria spp. treatments. The lowest body weight of chickens was recorded in treatment A3 (335.93 g). Results of feed consumption and feed conversion ratio showed some numerical differences between treatments but without any statistically significant differences (p > 0.05). Alternaria spp. contaminated diet increased glutathione (GSH), glutathione reductase (GR), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) and decreased peroxidase (POD) and superoxide dismutase (SOD) serum levels, respectively. Built on the achieved results, it can be concluded that the wheat contaminated with Alternaria spp. in broilers nutrition negatively affected growth, decreased oxidative protection and interrupted chicken welfare in the first period of life.