(1) Background: Targeting a sample of Chinese employees in this study, the correlation of work stress with changes in quality of life (QoL) was explored subsequent to acute coronary syndrome (ACS). (2) Methods: Patients suffering from the first ACS episode, with regular paid work before ACS, were eligible for this one-year longitudinal study. Effort–reward imbalance (ERI), together with job strain (JS) models, were employed to evaluate work stress before discharge, and QoL prior to discharge (baseline), as well as at 1, 6, and 12 months following discharge, were measured using the 8-Items Short Form (SF-8), in addition to the Seattle Angina Questionnaire (SAQ). Moreover, generalized estimating equations were used to determine the relationship of work stress to longitudinal QoL variations. (3) Results: After adjusting for covariates, high work stress at the baseline measured by JS was associated with the slow recovery of both mental health (p < 0.01) and physical health (p < 0.05) in SF-8, while ERI-measured work stress was related to slower improvement in SF-8 physical health (p < 0.001), SAQ-angina stability (AS) (p < 0.05), SF-8 mental health (p < 0.001), and SAQ-angina frequency (AF) (p < 0.05). After mutual adjustment for JS and ERI, high work stress as assessed by JS displayed no correlation with any QoL alteration (all p > 0.05), whereas ERI-determined work stress at a high level still presented a relationship to slow improvement in SF-8 physical health, SAQ-AS, SF-8 mental health, and SAQ-AF (all p < 0.05). (4) Conclusion: Work stress was associated with slow recovery of QoL in patients with ACS across one year. For ACS patients, ERI was a stronger predictor of QoL variations than JS.