In this study, we examine the mother tongue proficiency of pre-school children from high-income and highly educated families in Antalya, Turkey. The study used the Turkish version of the Hamburger Instrument for the Analysis of the Language Level of 5-year olds (HAVAS 5) linguistic-level diagnostic tool that is originally employed to form the basis of individually customized language support programs. The study group of this research was made up of 41 pre-school children (n= 41; 29 boys, 12 girls). Furthermore, a semi-structured interview (SSI) form was developed by the authors and finally conducted with 3 mothers and their husbands (n=6). Our study results show that the majority of the children (33/41) from high-income and highly educated families showed an advanced level of language proficiency especially in the realm of vocabulary acquisition. In particular, the children were observed to be self-confident when using their mother tongue and that they did not hesitate to take initiatives during the HAVAS 5 storytellings. Our qualitative results suggest also that a small group of children who are either introverts or having lower level language proficiency may have a specific trait, condition or characteristic. Based on the data from interviews, emotional atmosphere of the family, parenting styles, speech sound disorder (SSD) or excessive screen-based media use might reasonably be suspected of having some influence on mother tongue proficiency.