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PURPOSE To assess the associations of nighttime sleep duration and restlessness with the risk of multimorbidity in Chinese middle-aged and older adults. METHODS We used the 2011 and 2015 surveys of the China Health and Retirement Longitudinal Study (CHARLS). Sleep duration was grouped into ≤ 5, (5-6], (6-8], (8-9], and > 9 h/night. Restlessness days in the past week were categorized into < 1, 1-2, 3-4, and 5-7 days/week. Multimorbidity was defined as the co-existence of two or more of 14 chronic conditions (hypertension, dyslipidemia, diabetes mellitus, cancer, chronic lung disease, liver disease, heart problems, stroke, kidney disease, digestive disease, psychiatric problems, memory-related disease, arthritis, and asthma). Log-binomial regression models were used to estimate the associations. RESULTS A total of 6,037 participants free of multimorbidity at baseline were included. During four-years of follow-up, 2,203 (36.5%) participants developed multimorbidity. Compared to participants who slept 6-8 h/night, those with short sleep duration ≤ 5 h/night and 5-6 h/night were associated with 33.3% (95% CI: 14.8%-54.7%) and 24.2% (95% CI: 5.9%-45.6%) increased risk of multimorbidity, respectively. Long sleep duration was not significantly associated with incident multimorbidity. Compared to those who rarely or never had a restless sleep in the past week, participants with 5-7 days of restless sleep had increased risk of multimorbidity (RR: 1.750, 95% CI: 1.476-2.076). Similar findings were confirmed in subgroups by age, gender, and baseline chronic condition status. CONCLUSIONS Short nighttime sleep duration and restlessness were associated with increased risk of multimorbidity in China.