Grafting and foliar calcium application are common practices for improving vegetable crops, but their interactions in soil and soilless cultivation systems are not well understood. To address these knowledge gaps for sustainable greenhouse cucumber production, this study investigated the effects of calcium foliar application (control, 200 mg/L as nano-CaCO₃ or CaCl₂) and grafting (no grafting, grafting on Ganate rootstock or Routpower rootstock) on the growth and yield of greenhouse cucumber cv. Saba in soil and soilless systems. It should be noted that the two cultivation systems differed in several management factors (pot size, substrate, irrigation frequency, and fertilization method), and this study compares complete production packages rather than isolating individual factors. The experiment was conducted in a greenhouse using a factorial design with four replications. The results showed that the cultivation system was the dominant factor. Soilless cultivation significantly increased shoot fresh weight (307–344 g), plant height (265–326 cm), number of fruits (36–54 per plant), and fruit yield (2.7–4.5 kg per plant) compared to soil cultivation (shoot fresh weight: 177–216 g; yield: 0.4–1.0 kg per plant). Conversely, plants grown in soil had higher leaf dry weight percentage, root dry weight percentage, chlorophyll, and carotenoids. The effects of grafting were system dependent, with non-grafted plants performing as well or better in soilless culture, while grafted plants (especially Saba/Routpower combination) showed some soil-based advantages, including greater root length. Foliar calcium did not significantly improve most parameters, indicating that standard nutrient management provided sufficient calcium or that the 200 mg/L concentration was insufficient. Under the conditions tested, ungrafted plants grown without foliar calcium supplementation in soilless culture achieved yields comparable to more complex treatments, suggesting a simpler and more cost-effective production strategy.