<jats:title>Abstract</jats:title><jats:p>The 2011 Tohoku earthquake and tsunami in Japan was an extraordinarily stressful incident that caused harmful psychological reactions, such as posttraumatic stress disorder (PTSD), among affected individuals. However, a proportion of exposed individuals experienced posttraumatic growth (PTG), characterized by a noticeable degree of personal strength, spirituality, life appreciation, perception of new possibilities in life, and enhanced relationships with others. Some researchers have argued that these positive reactions may be an illusory change related to coping with traumatic events. We examined trajectory patterns related to PTG Inventory (PTGI) subscales to elucidate the existence of both real and illusory growth regarding quality of life (QoL), utilizing group‐based trajectory models. Three online questionnaires were distributed at 6 months (<jats:italic>N</jats:italic> = 2,554; <jats:italic>M</jats:italic> age = 47.04 years, <jats:italic>SD</jats:italic> = 12.62), 12 months (<jats:italic>N</jats:italic> = 887; <jats:italic>M</jats:italic> age = 48.11 years, <jats:italic>SD</jats:italic> = 12.43), and 42 months (<jats:italic>N</jats:italic> = 560; <jats:italic>M</jats:italic> age = 48.86 years, <jats:italic>SD</jats:italic> = 12.25) postdisaster. Participants responded to items related to demographic characteristics, disaster experiences, posttraumatic stress symptoms, PTG, and QoL. Three main PTG trajectories emerged, characterized by growth, no growth, and illusory growth, with QoL as a time invariant covariate. Compared with the growth trajectory, the odds ratios (<jats:italic>OR</jats:italic>s) for no growth ranged from 2.27 to 5.04; for illusory growth, the <jats:italic>OR</jats:italic>s ranged from 2.09 to 4.67. To our knowledge, this was the first study to report growth trajectories related to PTGI subscales and their underlying differences in psychological mechanisms and processes following the 2011 Tohoku earthquake and tsunami.</jats:p>