The transition of agricultural systems towards more sustainable models of production is necessary to meet the food security and nutrition needs of humans and the planetary health requirements of Earth.(1) Sustainable agricultural transitions can be supported with monitoring and measuring approaches like on-farm sustainability assessments.(2) Further, horticulture production contributes markedly to human core-food needs. The objective of this research was to undertake comprehensive sustainability assessments(2) using a co-participatory approach with horticulture producers. The research asked, what are the place-based barriers and enablers of sustainable horticulture production in rural Western Australia? A mixed-methods, comprehensive sustainability assessment instrument was implemented, data collection included: ten quantitative indicators (e.g., agricultural diversity) across environment, economic, social, human condition and production domains(3); a semi-quantitative agroecology questionnaire(4) and extensive qualitative interviews. The research adopted a case study approach, evaluating farms that incorporated horticultural production (n = 13). The cohort included a variety of annual and perennial (including tree crops) horticultural outputs such as fruits, vegetables and endemic bushfoods; however, most farms (n = 12) were mixed production and other outputs included livestock, eggs, honey, grains, viticulture and timber (agricultural diversity indicator range 3->100 output varieties). Farm size ranged from 4.6ha to 4500ha, respondents (n = 26, male = 13, female = 13, non-binary/another identity n = 0). Reflexive thematic analysis(5) identified that on-farm sustainability barriers and enablers were dynamic and case specific; for example, niche market access was a barrier in some instances and an enabler in others. Findings predominantly highlighted high-level structural factors and commercial determinants as important sustainability barriers: commercial governance factors (e.g., corporate-led compliance requirements) was increasingly challenging for smaller horticultural and mixed output producers; supermarkets dominated the fresh produce market; consumer and market influence determined produce aesthetics and production volumes, resulting in less sustainable agricultural practices (e.g., less investment in land-care, farming marginal land). Commercial drivers also led to high-volume production models requiring increased agricultural inputs (e.g., pest control, fertiliser) and reduction in agricultural diversity to meet market needs. Participants described how commercial drivers also resulted in niche production models that operated within the limited market margins beyond supermarkets. This mixed-methods research applied a comprehensive suite of indicators to examine horticultural sustainability, and raised potential risks to the production, availability and access to fresh produce; the systems-based findings connect sustainable horticultural production with food security and broader public health nutrition concerns. This research points to the need to move beyond the farm gate and to additionally account for structural factors, including commercial drivers and determinants, when considering agricultural sustainability. To protect Australian horticultural production for food security and nutrition, regulatory measures and a reorientation of market governance away from commercial-led governance, plus market-access support for smaller and mixed producers, may be necessary.