<p>This study aimed to estimate the age, period, and cohort trends of multimorbidity among Chinese older adults from 2002 to 2022, and to explore how these three trends were affected by gender and whether or not living alone. Data were extracted from the China Longitudinal Healthy Living Survey (CLHLS) (2002–2022), and a total of 52,876 valid samples aged 65 to 105 were included. We measured 15 types of chronic diseases, and participants having two or more chronic diseases were considered to have multimorbidity. Hierarchical age–period–cohort cross-classified random-effects model (HAPC-CCREM) was applied to examine the age, period, and cohort dynamics of multimorbidity. The average age of participants is 85.91 ± 11.09 years. The temporal effect of age on multimorbidity is inverted U-shaped, with a&#xa0;higher probability in women aged 65–95 years and in men aged 95–105 years. The cohort trends of multimorbidity showed a rise, then a fall, then a rise again, and the period trends declined in fluctuations. Gender differences existed in age and cohort trends of multimorbidity. Moreover, the interaction of gender and living alone was significantly associated with the age trends of multimorbidity. Women living alone have a lower risk of multimorbidity than women living with others among all age groups. This study revealed the separate effects of age, period, and cohort on multimorbidity. The peaks of multimorbidity probability for different genders occur at different ages, and living alone had a protective effect on females, which both provide a scientific basis for the allocation of healthcare resources. The dynamic shifts of multimorbidity may help to forecast future multimorbidity trends and inform policies on population aging.</p>