Background Cystic fibrosis-related diabetes (CFRD) is a common comorbidity reported in patients with cystic fibrosis (CF). There is a dearth of data on glucose intolerance or CFRD in children with CF from developing countries. So, we planned to study the prevalence of abnormal glucose tolerance (AGT) in children with CF and its relation with the duration and severity of CF. Methods We performed an oral glucose tolerance test (OGTT) on children (2-18 years old) having CF for at least 6 months. Two-hour plasma glucose levels on OGTT were correlated with various disease-related factors. Results Out of the 25 children enrolled, there were 18 boys and seven girls. The mean age and duration of CF were 7.9±4.3 and 3.16±2.5 years, respectively. AGT was observed in 16 (64%) children with CF including three (12%) children with CFRD. Children with a duration of CF of 3 years had significantly higher prevalence (81.8%) of AGT when compared with duration ≤3 years (p-value<0.05). Twelve out of 17 (70.6%) children were colonized with Pseudomonas and 12 out of 15 (80%) children >6 years of age had AGT. There was a positive correlation of 2-h glucose value on OGTT with duration of CF and number of hospitalizations with acute pulmonary exacerbations. Conclusions The majority of children having CF for >3 years and/or age >6 years developed AGT. In our clinical setting, an annual screening with OGTT to detect AGT may be required at an early age and duration of CF.