The association between indoor air quality (IAQ) and sleep quality was investigated in this study. A total of 27 participants (14 males and 13 females, 20-33 yrs.) without any sleep disorders and chronic diseases were recruited and divided into two groups: a polysomnography (PSG) group and a non-PSG group. The IAQ was changed by opening or closing windows. There were two phases for the experiment and two nights in each phase including one adaptive night and one test night, and around one-week washout period between two phases. A questionnaire, Fitbit and home PSG – the Nox A1 (from Resmed) were used for measuring sleep quality. Bed temperature, ambient temperature, relative humidity, CO2 levels, TVOCs, PM2.5 and noise were recorded by different sensors during sleep. Mann-Whitney U tests and multivariate linear regression models were used for statistical analyses and individual differences between two phases were also analyzed. Higher ambient temperature, RH and CO2 levels were monitored with the window closed compared to it open. The participants had on average a 0.87 point higher score on the Groningen sleep quality scale (GSQS) sleeping with the window open than with it closed. Higher PM2.5 levels were associated with time awake (β, 95% CI: 1.546, 0.124 - 2.968; p-value < 0.035), percentage awake (β, 95% CI: 0.342, 0.091 - 0.592; p-value < 0.010) and sleep efficiency (β, 95% CI: -0.342, - 0.592 - -0.091; p-value < 0.010). Higher ambient temperature was associated with the number of awakenings (β, 95% CI: 3.074, 0.331 - 5.816; p-value < 0.030). In conclusion, the participants reported better sleep quality sleeping with quieter surroundings (windows closed). Higher PM2.5 level was associated with more time awake, higher percentage awake and lower sleep efficiency. Higher ambient temperature was associated with an increased number of awakenings.