Sleep hygiene includes behaviours and environmental conditions that promote restful sleep, and adolescents are particularly at risk for poor sleep due to circadian rhythm changes, academic pressure, and increased screen use. This quantitative descriptive correlational study assessed sleep hygiene and academic performance among 60 adolescents aged 13–16 years in a private school in Velachery, Chennai, using a socio-demographic questionnaire, Sleep Hygiene Index (SHI), and academic scores. Results showed that 66.7% had moderate sleep hygiene, 31.7% good, and 1.7% poor, while 45% scored above 75% academically, 43.3% between 51–74%, and 11.7% below 50%, with mean SHI score of 33.75 (SD = 5.76) and mean academic score of 57.43 (SD = 7.51). A strong positive correlation (r = 0.92) was observed between sleep hygiene and academic performance, though no significant associations were found with demographic variables at the 0.05 level. Despite limitations such as small sample size, convenience sampling, cross-sectional design, and reliance on self-report, the findings suggest that better sleep hygiene is associated with improved academic outcomes, highlighting the need for sleep hygiene education and further research using larger samples and experimental approaches.