Context: Rainfed agriculture faces a high risk of crop failure due to intermittent dry spells during crop growth period. In water scarce regions, rainwater harvesting (RWH) structures offer significant benefits for sustainable solution by storing rainwater and serving as a source of supplemental irrigation (SI). Objective: This study evaluated the critical design parameters of RWH structures (i.e., farm ponds and mini-dams), and their impact on crop production through SI, and potential of integrating fish farming. Methods: Crop yield and productivity data were collected from two growing seasons (2019-2020). While demographics, fish production, economics of RWH structures, and on-farm practices were collected through field observations, questionnaires, and key informant interviews. The design parameters of selected RWH structures were collected from feasibility reports, whereas catchment features were extracted from a digital elevation model (DEM) using ArcSWAT extension in ArcGIS. Results and conclusions: The results showed that, on average, SI significantly improved the wheat yield by 146 %, mustard by 101 %, maize by 118 %, and pearl millet by 101 % compared to rainfed yields. The average irrigation water productivity for these crops ranged from 0.96 to 3.18 kg m-3 compared to rainwater productivity ranged from 0.19 to 0.76 kg m-3. On average, fish production of 5322 kg from a mini-dam was significantly higher compared to a farm pond (2549 kg). The economic analysis revealed that cost of constructing a mini-dam was US $ 27,543 compared to US$ 11,489 for farm pond, while average cost of harvesting a m3 of rainwater was US$ 0.55. Benefit-cost ratio analysis further confirmed that investing in RWH structures is a financially viable option. Significance: This study addresses the water scarcity challenges in rainfed agriculture by demonstrating how RWH structures can sustain crop production during dry spells through SI, while integrating fish farming further improves farm income.