The importance of events to individual experiences and behaviour within organizational research is increasingly acknowledged. This research examines whether daily positive and negative affective HRM events signal employee perceptions of HRM system strength, which are expected to relate to daily work engagement via clear performance–reward expectancies. Employees completed a daily diary over ten working days and reported positive and negative daily HR events as they arose. Positive HR events associated with higher perceived event-signalled HRM system strength compared with negative HR events, and expectancy perceptions partially mediated the effects of perceived HRM system strength on daily work engagement. The study’s novel contributions include documenting the common occurrence of affective HRM events, identifying such events as an important antecedent to perceived event-signalled HRM system strength, and extending understanding of the daily consequences of perceived HRM system strength by showing how their effects on daily work engagement are mediated by expectancies.