Purpose: To analyze the performances of 2 ultra-triathletes who competed in ultra-triathlon events (double Iron ultra-triathlon and triple Iron ultra-triathlon) for the past 3 decades. Longitudinal data of the performance development in ultra-triathlon athletes spanning many years are rare. Prediction of age-related performance declines in the different disciplines in triathlon events (swimming, cycling, and running) are needed for race directors to set realistic goals (time limits) for master athletes in these events. Methods: Athletes A and B had 34 and 53 participations in double Iron at 35–55 and 40–69 y of age, respectively, and 26 and 20 participations in triple Iron at 33–51 and 40–61 y of age, respectively. Nonlinear regression analyses were performed with split and overall performance against age. Results: The average declines in performance in triple Iron ultra-triathlon for athlete A were 0.62%/y, 0.19%/y, and 0.98%/y for swimming, cycling, and running, respectively. For athlete B, a positive change was identified for swimming (0.19%/y) and cycling (1.12%/y) but negative change for running (1.34%/y). Conclusion: Running is the discipline with the greatest performance-decline rate for both athletes, in both double and triple Iron distances. The race time limit of double Iron competitions seems too short, making it difficult for master athletes older than 55 y to finish the race within the event regulations.