The study aimed to investigate health-related knowledge, attitude, practice (HR-KAP), and quality of life (HRQoL) among diabetes and hypertensive patients at Damak municipal hospital, Province 1, Nepal. A cross-sectional study was conducted in the medicine outpatient department of Damak Municipal Hospital from April- September 2022. The participants' HR-KAP was assessed using a 23-item self-administered questionnaire, and their HRQOL was determined using the EuroQoL-5 dimensions (EQ-5D-5L) questionnaire. Independent sample test and chi-square test were used to measure the association between patients characteristics and outcome variables. P value <0.05 was considered statistically significant. A total of 105 patients with a mean age of 49.40 (±11.11 SD) years participated in the study. Although 49.5% of the patients demonstrated good disease knowledge, their attitudes and practices toward the diseases were found to be poor, accounting for 30% and 19%, respectively. The KAP score was significantly associated with the patients age group, gender, and patient education status (p<0.05). The majority of patients reported mild or moderate problems in morbidity, usual activities, pain/discomfort, and anxiety/depression with the average EQ-5D-5L index value and EQ-VAS scores of 0.78 (±0.09 SD) and 58.43 (±10.882 SD) respectively. The HRQoL was comparatively lower among age groups over 65 years, female gender, and illiterate patients (p<0.05). The study concludes that patients’ HR-KAP toward their disease was inadequate and had diminished HRQoL. There is an urgent need for health educational and interventional programs particularly focusing on chronic diseases such as diabetes and hypertension to people in this area.