Background: Gestational diabetes mellitus (GDM) is a serious pregnancy complication, in which women without previously diagnosed diabetes develop chronic hyperglycemia during gestation (Plows, 2018). Along with various adverse maternal and neonatal complications during pregnancy, there are long term consequences like obesity and risk of diabetes mellitus (DM) following diagnosis of GDM. Objectives: This study was undertaken to assess the effectiveness of information booklet regarding GDM on knowledge among pregnant women with diabetes. Material & methods: The research approach was quantitative and pre experimental with one group pre test post test only design was applied in the study. Samples of the study were the admitted pregnant women who have been diagnosed with GDM, met the inclusion criteria and agreed to participate in the study. In this study, one group of 70 patients were selected by using consecutive sampling technique. After taking informed consent the pre test was taken and later participants were provided with information booklet on GDM. One week later the post test of the participant was taken. The collected data was analyzed by descriptive (frequency distribution and percentage) and inferential statistics. Result: Results of the study showed that the pre test knowledge score among study subjects were 28(40%) have good knowledge score, 36 (51.4%) have average knowledge scores score while 6(8.6%) have poor knowledge score. Thus majority of participants had average knowledge level in pre test. There was significant improvement in overall knowledge scores from 13.59 in pre test to 16.69 in post test as well as in all aspects of knowledge regarding gestational diabetes mellitus at p < 0.001 which showed that informational booklet regarding gestational diabetes mellitus was highly effective. There has been significant association was found between pre test knowledge score and area of residence at p value 0.021 as well as with education level at p value <0.001. Conclusion: The study found that imparting information booklet is effective way to improve awareness and understanding about GDM. As nurses play very important role in providing health education to patients they can use these kind of booklets in giving health education as knowledge gained through informational booklet regarding GDM may improve the self care practices among diabetic pregnant women .