Gestational diabetes mellitus (GDM) is a common metabolic disorder during pregnancy requiring careful pharmacological management to prevent maternal and fetal complications. Drug-related problems (DRPs) may compromise therapeutic outcomes and increase adverse events. This prospective interventional study aimed to identify DRPs and evaluate the impact of structured patient counselling using the Appraisal Diabetes Scale (ADS). The study was conducted over six months in a tertiary care teaching hospital involving 100 pregnant women diagnosed with GDM. DRPs were categorized as adverse drug reactions, dosing problems, drug interactions, and non-adherence. Patients were divided into intervention and control groups. Baseline ADS scores were assessed, followed by structured pharmacist-led counselling for the intervention group. Post-intervention assessment was performed. A total of 32 drug related problems (DRPs) were identified among the participants, with adverse drug reactions being the most frequently reported. Post-counselling assessment showed improvement in ADS scores and better disease perception in the intervention group compared to control group. The study concludes that structured clinical pharmacist counselling significantly reduces DRPs and improves medication adherence and disease perception among pregnant women with GDM.