Workplaces are inherently emotional spaces, where employees often attempt to influence others’ feelings. While effective interpersonal emotion regulation benefits relationships and performance, older workers’ capabilities in this domain remain poorly understood. Drawing on lifespan development theories, we hypothesize that employees’ motivation to regulate others’ emotions, their use of adaptive regulation strategies, and their effectiveness at implementing interpersonal emotion regulation are all positively related to age. We further explore the moderating role of two contextual factors: the intensity of workers’ own negative emotions and their perceived closeness to the target of regulation. We tested hypotheses using a pre-registered, five-day experience-sampling study with 219 participants who completed surveys twice daily during their working day. Results show that age is positively associated with motivation to regulate others’ emotions and perceived implementation effectiveness but is unrelated to strategy use. Exploratory analyses indicate an indirect effect of age on perceived effectiveness of interpersonal emotion regulation, via motivation. Neither relational closeness nor negative emotion intensity moderates the effects of age. These findings extend lifespan theories to the interpersonal domain, suggesting that ageing is more strongly related to why, rather than how, employees regulate others’ emotions, positioning motivation as a critical yet overlooked strength of older workers.