Although numerous studies have examined caregiver burden in the context of Alzheimer's disease, discrepancies remain regarding the influence of certain factors. This study aimed to identify trajectories of caregiver burden in the context of Alzheimer's disease, as well as the factors associated with them. A cohort of patients and caregivers (n = 330) was followed up over three years. Growth mixture models were fitted to identify trajectories of caregiver burden according to scores on the Zarit Burden Interview (ZBI). A multilevel multinomial regression analysis was then conducted with the resulting groups and the patient and caregiver factors. In the sample as a whole, burden increased during follow-up (F = 4.4, p = 0.004). Three groups were identified: G1 (initially high but decreasing burden), G2 (moderate but increasing burden), and G3 (low burden that increased slightly). Patients in G1 and G2 presented more neuropsychiatric symptoms and poorer functional status than did those in G3. Caregivers in G1 and G2 had poorer mental health. Spouses and, especially, adult children who lived with their parent (the patient) were more likely to belong to G2 (odds ratio [OR] 6.24; 95% CI 2.89-13.47), as were sole caregivers (OR 3.51; 95% CI 1.98-6.21). The patient factors associated with increased burden are neuropsychiatric symptoms and functional status, while among caregivers, being the sole carer, poor mental health, and living with the patient are of relevance.