Diverticular disease is a common gastrointestinal disorder with increasing prevalence in advanced age. This study aimed to investigate the impact of age and complexity of diverticulitis on health-related quality of life (HRQoL) and stress-related disorders. A cross-sectional study was conducted on 180 patients, including adults (18–64 years) with complicated diverticular disease, the elderly (≥65 years) with complicated diverticular disease, and a control group with uncomplicated symptomatic diverticular disease. HRQoL and stress-related disorders were assessed using the SF-36, GIQLI, HADS, and PHQ-9 questionnaires at baseline and six months after the initial episode of diverticulitis. At diagnosis, the adult group had significantly lower mean physical and mental scores compared with the elderly and control groups (p< 0.001). At the 6-month follow-up, the mean physical score increased for all groups, but the difference between adults and the elderly remained significant (p= 0.028). The adult group had a significantly lower mean GIQLI score at diagnosis compared with the elderly and control groups (p< 0.001), although after 6 months it increased and the difference became insignificant. Anxiety scores at diagnosis were significantly higher in the adult group compared with the control group (p= 0.009). The complexity of diverticulitis and age significantly impacted HRQoL at diagnosis, with adults having lower physical and mental scores compared with elderly patients and controls. Although improvements were observed after 6 months, the difference between adults and the elderly remained significant for physical HRQoL scores. This highlights the need for tailored management strategies and psychosocial support to optimize patient outcomes across age groups and diverticulitis complexity.