<b><i>Introduction:</i></b> The Multidimensional Prognostic Index (MPI) is a validated tool for assessing mortality risk in hospitalised patients. We aimed to evaluate whether the MPI predicted mortality and the risk of developing diverticular disease (DD) complications in older patients. <b><i>Methods:</i></b> This is a multicentre study conducted in January 2016-March 2018. All patients with DD aged 65 years and older were included. Patients were stratified into three groups according to MPI groups (1, low risk; 2, moderate risk; 3, high risk). Risk of developing DD complications and mortality rate were assessed. Bivariate models were fitted. <b><i>Results:</i></b> One hundred hospitalised patients with DD (mean age 77.9 ± 10.6 years, 53 female patients) were included. Patients with higher MPI groups were more likely to develop DD complications. In particular, 12 (46.2%), 21 (52.5%), and 28 (82.4%) patients with complicated DD were distributed to the MPI 1, MPI 2, and MPI 3 groups (<i>p</i> = 0.0063), respectively. Two patients died in the MPI 1, 4 in the MPI 2, and 29 in the MPI 3 group, with mortality rates of 4.0 per 100 person-year (95% confidence interval [CI] 1.0–15.9), 5.6 (95% CI 2.1–15.0), and 89.2 (95% CI 62–130), respectively (log-rank test <i>p</i> &#x3c; 0.001). In bivariate analysis, after adjustment for age &#x3e;80 years, Charlson Comorbidity Index &#x3e;4, DD complications, and the presence of thromboembolism, higher MPI group was independently associated with higher mortality. Those in the MPI 3 group experienced a greater risk of 1-year hospital readmission (<i>p</i> &#x3c; 0.001). <b><i>Conclusion:</i></b> MPI predicted mortality in patients with DD and also correlated with the risk of developing DD complications. Studies focussing on possible pathophysiological mechanisms between DD complications and MPI are needed.