Cultivation of indigenous crops for food and nutritional security has emerged as a topic of interest in South Africa. Commercial cultivation of indigenous crops is promoted especially among smallholder farmers because of their nutritional value and their ability to adapt to marginal soil and climatic conditions. Support for commercial production of specific crops among farmers necessitates the need for optimum use of inputs in production. In order to evaluate optimum input use in production, this study established the profitability and production costs of one of the indigenised leafy vegetables in South Africa, Chinese cabbage, using gross margin analysis. Production costs and profitability evaluations are fundamental tools for analysing cash flow and investment options. The study was based on field trials on different levels of fertilizer (NPK application). The results of the study show that at low production level (10.1 t ha-1), gross income is less than total variable costs (TVC), resulting in a negative gross margin. A movement from low production to medium production (26.1 t ha-1) results in an increase in gross margin, from -R16,664.19 to R29,091.99. The highest gross margin of R82,807.07 is obtained at high production level (44.5 t ha-1). The study supports an interdisciplinary evaluation approach (agronomy and economics) when analysing field trials.