Early diagnosis is extremely important for children with autism spectrum disorder (ASD), as other children having developmental disabilities. In early diagnosis, which is one of the most important elements of the treatment process, parents have a special place with different factors. Considering the importance of parents in early diagnosis, the aim of the study is to examine the opinions of the mother on early developmental differences in children with autism. The research is a case study designed in a qualitative research model. Accordingly, an interview form was developed by the researchers and data were collected in the scanning model in the first step of the study. In the second step of the study, data were obtained by using the semi-structured interview method, which is one of the qualitative research methods. In the study group of the research, 110 mothers were interviewed, whom were selected via purposeful sampling, and 87 mothers, who gave full answers to the questions, were included in the study. The data obtained were subjected to descriptive and thematic analysis. As a result of the study, it was found that children diagnosed with autism and children with development showed similar developmental characteristics during pregnancy and after birth. It was observed that mothers with a child diagnosed with autism have the awareness on the suspicion of autism in their children when they are between 18 and 24 months and 31 and 36 months, and they experienced problems in breast-feeding and falling asleep.