Sleep quality significantly impacts both mental and physical well-being. Sleep disorders are prevalent, especially among medical students, who often overlook the importance of good sleep. This study aimed to examine sleep quality, assess happiness levels, and explore the relationship between sleep quality and happiness among preclinical students. A cross-sectional study was conducted with preclinical students (Year 1 and Year 2 of Bachelor of Medicine and Bachelor of Surgery) from Manipal University College Malaysia. An online questionnaire was distributed, covering demographic data, sleep quality (measured using the Pittsburgh Sleep Quality Index), and happiness (assessed using the Oxford Happiness Questionnaire). Data were analyzed using Microsoft Excel and SPSS, with multiple linear regression used to evaluate the relationship between sleep quality and happiness. A sample of 305 participants, comprising 66.6% females and 33.4% males, participated in the study. Sleep latency analysis revealed that 25.9% of students fell asleep within 30-45 minutes, while 6.2% took 5-6 hours. Most students (55.4%) rated their sleep as fairly good, and 43.3% slept 6-7 hours per night. A significant majority (81.3%) had high sleep efficiency (>85%). The study found that 66.6% experienced minor sleep disturbances. The happiness score revealed that 53% of participants were moderately happy, with family playing a crucial role in their happiness. In the multiple linear regression analysis, the p-value for subjective sleep quality was 0.005, and for daytime dysfunction, it was less than 0.001. Both subjective sleep quality and daytime dysfunction scores significantly predicted happiness levels.: A significant association was found between subjective sleep quality, daytime dysfunction, and happiness. Preclinical students with better sleep reported higher happiness levels. Interventions to improve sleep quality, such as counselling sessions, may enhance student well-being and academic performance.