Objective This study aimed to (1) identify the changes of 5 domains of family caregiver (FC) burden, overall burden, and its subtrajectories when caring for newly diagnosed advanced lung cancer patients during the first 6 months following cancer diagnosis; and (2) identify the FC‐related and patient‐related factors most associated with the overall FC burden and each of its subtrajectories. Methods A total of 150 newly diagnosed advanced lung cancer patient‐FC dyads were recruited from a Taiwanese medical center.