We assessed the relationship between physiological and psychological measures of workplace stress as measured by the effort-reward imbalance (ERI) model, with a seldom studied sample of owner-operator dairy farmers. Dairy farmers (N = 74) self-reported ERI, over-commitment (OC), dedication, and health then provided awakening saliva samples that were used to calculate the salivary alpha amylase awakening response (sAA-AR), cortisol awakening response (CAR), and salivary immunoglobulin A (sIgA) level. ERI, OC, and dedication levels were not related with sIgA or the CAR, but more over-committed farmers had a less pronounced sAA-AR. OC was more associated than ERI with the physiological indicators of stress, potentially due to the owner-operator sample used in this investigation. The suitability of sAA as a viable physiological measure of autonomic nervous system activity has been debated, but our findings promote its inclusion in future occupational stress research.