The transgenic maize DBN9936 × DBN9501, which confers resistance to insects and tolerance to herbicides, was developed via conventional cross breeding of transgenic maize DBN9936 and DBN9501. In our present study, a 90‐day feeding toxicity study was conducted on Sprague Dawley rats to evaluate the safety of the maize. A total of 140 rats were randomly assigned to seven groups (n = 10/sex/group): one control group, three genetically modified (GM) groups with 17.5%, 35%, and 70% (wt/wt) GM maize, respectively, and three non‐GM groups with corresponding incorporation rate of parental maize DBN318. The rats of control group were fed with AIN93G diet. The parameters including body weights, food consumption, hematology, serum biochemistry, organ weights, and histopathology were examined during the course of the study. Compared with the non‐GM group or AIN93G control group, minor statistical differences were observed for some parameters in some groups, yet none of them was considered a GM‐related adverse effect. In conclusion, the results demonstrated that no adverse effect was observed on rats following 90 days feeding with diet containing up to 70% GM maize. The results indicated that stacked maize DBN9936 × DBN9501 was as safe as its parental DBN318 maize.