Objective To ascertain whether modifiable physical performance-based measurements predicted 5.5-year mortality in a riparian elderly cohort in the Amazon rainforest region. Methods A longitudinal study evaluating the impact of functional determinants on 5.5-year mortality in a riparian elderly cohort from Maués City in the state of Amazonas, Brazil, was performed. The study was a follow-up of a previous observational investigation that evaluated various fitness tests in 630 Amazonian riparian elderly (291 males and 339 females) aged 72.3 ± 8.0 (60-99) years old. The cohort was selected for its adverse environmental conditions, which increased the risk of falls yet required maintenance of good physical condition for carrying out relatively rigorous daily activities, and restricted access to specialized health services. Official death records were obtained from the Maués Municipal Health Department. Results A total of 80 study participants (12.7%) died over the 5.5-year study period. Kaplan-Meier regression analysis showed significant association between Timed Up and Go (TUG) test scores ≥ 14 seconds and mortality risk, independent of sex, age, and other health variables. Conclusions The study results suggest that the TUG test can be used as an indicator for initiating therapeutic and preventive actions, including conducting exercises or physical activities adapted to the health and functional conditions of the elderly, by identifying elderly people with a higher relative risk of mortality.