Down syndrome (DS), one of the developmental (cognitive) deficits, is the most common syndrome that arises from genetic disorders. The mothers of children with DS who encounter the most intense emotional situations since the tendency to take responsibility the children's care and development usually belongs them. Among these intensive feelings, mothers are also responsible for providing needs, such as special education support, searching for a suitable preschool institution to accept their children, and access to specialists who can understand their medical needs. This case study aims to investigate the opinions of the mothers whose children with DS aged between 36-72 months were attending preschool. The data were collected using semi-structured interview techniques in three different preschool institutions where the mainstreaming was carried out in the district center of Gaziantep, Sahinbey. Interviews were conducted with five mothers whose DS children went to the preschool institution in the spring semester during 2015-2106 academic year. Descriptive and content qualitative analyses were used to analyze the data. The findings regarding the opinions of the mothers of DS children on the quality of the mainstreaming practices revealed the following salient themes: Early experiences before mainstreaming, quality of mainstreaming at preschool and inclusion. The findings showed that inclusion practices have not been adopted in mainstreaming practices in our country; therefore, the most reliable sources mothers preferred to follow was the experienced families who had children with DS in the preschool.