PurposeGlobal developmental delay (GDD) is highly prevalent among patients at child psychiatry clinics. However, preschool day treatment centers are currently scarce. As such, this study aimed to evaluate a program that was designed for children with GDD in order to improve their global skills and prepare them to join the school system.Design/methodology/approachThis study utilized an observation retrospective design with a comparative group sample and included all children aged between 3 and 6 years who participated in the program for at least one academic year (experimental group). Their GDD diagnoses were based on the DSM-5 criteria (Diagnostic and Statistical Manual of Mental Disorders). Children with similar diagnoses who were on the waiting list constituted the control group. Pre- and post-scoring of the Children’s Global Assessment Scale (CGAS) were conducted by the children’s teacher and blinded investigator for the experimental group, while the children’s mothers conducted the post-CGAS scoring for the control group.FindingsThe pre- and post-CGAS scores for the experimental group were 49.5 ± 12.8 and 58.3 ± 12.7 and 47.3 ± 17.3 and 66.6 ± 17.3 for the control group, respectively (p = 0.001). The children in the experimental group scored significantly better than the control group with respect to securing places in integrated, regular classes in the education system (p = 0.001).Research limitations/implicationsThis study had certain limitations. First, the number of children in the control group was relatively small. Second, the baseline skill levels of some of the children in the control group may have been lower than those of the children in the experimental group at the beginning of the evaluation; this may explain why they had been put on the waiting list. Third, the information was gathered retrospectively; this is a method that is known to have its own limitations.Practical implicationsThe clinical implications of the study are that the early identification and referral of GDD are key elements in the rehabilitation of these children and that early intervention programs are necessary for cases of moderate and severe GDD. Primary care physicians should follow up with GDD patients to ensure that referrals are being appropriately sought (Choo et al., 2019).Originality/valueThe program was effective in both increasing the general functioning skills of the children in the experimental group and preparing them to attend regular, integrated classes. The program should be expanded and made available to more children with GDD.