Background: Up to 55% of health system greenhouse gas emissions are estimated to come from pharmaceuticals, contributing to climate change. There is limited understanding of how pharmaceutical companies mitigate their climate impact. My research explored how multinational pharmaceutical companies approached climate action and what might support net zero progress. Methods: Guided by Maarten Hajer’s argumentative discourse analysis, I analysed data from purposively sampled (a) company documents from three selected multinational pharmaceutical companies, and (b) narrative interviews with twenty-one representatives from these companies, industry groups, and health systems. Argumentative discourse analysis studies the discursive production of meaning about phenomena and the practices through which discourses are produced, reproduced, or transformed. Key analytical concepts include (a) storylines, condensed statements underpinned by various discourses, the ensemble of ideas and concepts through which meaning is ascribed to phenomena; (b) counter-storylines, condensed statements that challenge storylines; (c) discourse-coalitions, actors sharing storylines; and (d) discourse institutionalisation, the solidification of discourse into institutional practices. I extended my analysis with concepts from impression management theory, which sensitised me to the performativity of pharmaceutical company climate action. Findings: I identified four storylines and counter-storylines, underpinned by distinct discourses. (a) Climate action conflicts with patient wellbeing, underpinned by a biomedical discourse prioritising patient care typically via pharmaceuticals, through which pharmaceutical climate impact and inaction was legitimised. A counter-storyline, reflecting planetary health discourse, framed climate action as integral to patient wellbeing. (b) Climate action is contingent on financial viability, advanced by pharmaceutical actors drawing on economic discourse to frame climate action through financial terms. Health system actors challenged this through a counter-storyline, using normative discourse to advocate for climate action regardless of financial viability. (c) Climate action as emissions quantification and disclosure, underpinned by technocratic discourse through which emissions data was framed as vital for compliance and to inform climate action. A counter-storyline, grounded in post-technocratic discourse, critiqued over-reliance on data, urging focus on emissions reduction. (d) Climate action requires more collaboration, drawing on techno-optimist and network governance discourses, climate action was framed as solvable through collective innovation and shared responsibility. Calls for collaboration often remained vague or served to displace responsibility. Conclusion: Dominant discourses, institutionalised in practice, collectively framed pharmaceutical company climate action as conditional on ensuring patient wellbeing, financial viability, access to emissions data, or increased collaboration, thereby delaying and constraining net zero progress. Acceptance, reproduction, and institutionalisation of counter-storylines and alternative discourses by key actors offers potential to support net zero progress, by reframing climate action as interconnected with patient wellbeing, decoupling it from profit, shifting emphasis from quantifying emissions to reducing them, and facilitating productive collaboration.