The main concerns for agricultural production nowadays are excessive crop cultivation, water scarcity, and poor soil quality. It is possible to amend agronomic soil with activated biochar (BC) to achieve high water-fertilizer availability and Camelina crop production under rainfed conditions by using an efficient and environmentally safe technology. A split plot experiment was arranged on a randomized complete block design with nine treatments and three replications. The main and second factors were supplementary irrigation (SI) and BC, respectively, with SI comprising of no irrigation (control), irrigation at the flowering stage and seed-filling stage, while BC included control (BC0), 5 (BC5), and 10 (BC10) t ha−1. The number of lateral branches and seeds in the silique, seed yield (2751.8 kg ha−1), 1000-seed weight (1.16 g) and oil yield (991.50 kg ha−1) were highest in response to irrigation at the flowering stage and the application of BC10. The gas chromatography analysis showed that the highest amount of unsaturated fatty acids (oleic, linoleic, linolenic, eicosadienoic and palmitic acids) was obtained in response to BC10 and irrigation at the seed-filling stage. Finally, the results showed that BC10 and the application of SI at the flowering stage increased the seed and oil yield, and unsaturated fatty acid content in Camelina. This study demonstrates that BC amendments can improve plant performance and preserve the environment, with significant implications for the alleviation of drought and sustainable Camelina production in arid regions. The study provides a practical way to produce Camelina in rainfed areas, which can benefit farmers economically.