Background <p>This study aimed to determine the frequency and amount of consumption of caffeine-containing foods among adults in active employment and to examine the relationship between total daily caffeine intake and sleep quality.</p> Methods <p>This cross-sectional study included 428 working adults aged 19–50 years. Caffeine intake was assessed using a quantitative consumption frequency form created by the researchers, while sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI). Statistical analyses involved appropriate parametric and nonparametric tests, as well as correlation and multiple linear regression models.</p> Results <p>The participants’ average daily caffeine intake was 262.5 [144.0-411.0] mg. The primary sources of caffeine were black coffee (filter/Americano), black tea, and Turkish coffee. Participants with poor sleep quality (71.7%) consumed significantly more caffeine daily than those with good sleep quality. A positive and significant correlation was observed between caffeine intake and PSQI scores. Regression analysis indicated that caffeine consumption, was a significant independent predictor of poor sleep quality (β = 0.147, <i>p</i> = 0.003), particularly affecting sleep duration and disturbances.</p> Conclusion <p>These results suggest that caffeine intake is a significant lifestyle factor independently associated with sleep quality, and a comprehensive evaluation of consumption sources could benefit public health. Future research should also focus on the timing of caffeine consumption and incorporate objective sleep measures.</p> Graphical Abstract <p></p>