Background Recent research reveals that not all job demands have negative effects on workers’ well-being and suggests that the negative or positive effects of specific job demands depend on the occupational sector. Specifically, emotional job demands form the heart of the work for nurses and for this reason they can be interpreted by nurses as a challenge that promotes motivation and well-being among these professionals, especially if personal and job resources become available. Objectives The study had two objectives. First, to examine whether daily emotional demands within a nursing work context have a positive effect on nurses’ daily motivation at work (vigour) and well-being at home (vitality and positive affect). Second, to explore whether this positive effect could be enhanced by nurses’ emotional regulation abilities. Design This research used a diary design to explore daily experiences and to analyze how variations in specific job or personal characteristics can affect levels of motivation and well-being across days. Participants Fifty three nurses working in different Spanish hospitals and primary health care centres completed a general questionnaire and a diary booklet over 5 consecutive working days in two different moments, after work and at night (N = 53 participants and N = 265 observations). Results In line with our hypotheses, multi-level analyses revealed that, on the one hand, day-level emotional demands at work had a positive effect on vigour at work and on vitality at home. On the other hand, analyses showed that nurses with higher emotional regulation abilities have more motivation at work and well-being at home when they have to face high emotional demands at work, showing a spill over effect after work. Conclusions These findings support the idea that emotional demands from the nursing profession can act as challenges which promote motivation and well-being, especially if internal emotional resources become available.