Work is often seen as either a source of fulfillment or a cause of harm and exhaustion. Stéphane Moulin rejects this binary, arguing that well-being at work is fundamentally ambivalent. Placing ambivalence at the centre of his analysis, Moulin calls for a rethinking of well-being at work and a renewed dialogue between psychological and sociological approaches. Drawing on survey data from 579 workers in Quebec's restaurant and academic sectors, as well as in-depth interviews with restaurant supervisors and academic chairs, Moulin examines work experiences across academic roles - from professors and professional staff to lecturers and support staff - and restaurant occupations - from supervisors, servers, and cooks to kitchen and service helpers. He identifies three ambivalent profiles - the overworked, the disappointed, and the serene - situated between the marginal extremes of the morose and the satisfied. This ambivalence arises from three forces: ongoing psychosocial exposure shaped by the uneven fulfillment of workplace justice needs; ethical dispositions, notably hard work and resilience, sustaining effort while masking harm, alongside distinct work ethos marked by tensions unique to each social world;; and management strategies, including self-management, that privilege short-term coping over structural change and reveal an insidious colonization of personal life by work. With its original, empirically grounded analytical framework, The Ambivalence of Well-Being in the Workplace invites a rethinking of the human relationship to work.