Failures to realise delayed intentions (prospective memory, PM) are common in everyday life,yet little is known about how PM performance can be improved. Deeper encoding duringintention formation has been proposed to strengthen memory representations and facilitatelater retrieval; however, no study has systematically compared different encoding strategiesfrom childhood to middle adulthood. To address this gap, we examined the effects of twoencoding strategies – episodic future thinking (EFT; mental practice) and enactmentencoding (EE; physical practice) – on PM performance across four age groups. A total of 373participants were tested, including children (n = 90), adolescents (n = 96), young adults (n =97), and middle-aged adults (n = 90). Participants were randomly assigned to an EFT, EE, orstandard encoding condition and completed a novel computerised PM task. A significantmain effect of encoding condition emerged. Overall, participants in the EE conditionoutperformed those in both the EFT and standard encoding conditions, with no evidencethat this benefit differed by age group. Contrary to expectations, EFT did not improve PMperformance relative to standard encoding. This unexpected finding is discussed in terms ofcue focality and high ongoing task demands.