We investigated a new phenomenon that sheds light on age-related differences in strategy selection: the strategy repetition phenomenon (i.e., tendency to repeat the same strategy over consecutive items). Young and older adults had to provide the best estimates of multiplication problems like 47 x 86. They had to select the best of 2 rounding strategies on each problem, the rounding-down strategy (i.e., doing 40 x 80 = 3,200) or the rounding-up strategy (i.e., doing 50 x 90 = 4,500). Data showed that both young and older adults repeated the same strategy over consecutive problems more often than chance and repeated strategies more often in the 2-prime condition (i.e., after executing one strategy to solve the 2 immediately preceding problems) than in the 1-prime condition (i.e., after executing a strategy on one immediately preceding problem). Moreover, this strategy repetition phenomenon increased with age, especially in the most difficult condition (e.g., when participants solved rounding-up problems in the 2-prime condition). Our findings have important theoretical and empirical implications for computational models of strategy selection and for furthering our understanding of strategic development during adulthood.