Deficit irrigation has been widely studied on fruit quality improvement, but it also leads to yield losses, especially, fruit size reduction. The objective of this study was to investigate if the silicon application could offset the negative influence brought by deficit irrigation while enhancing fruit quality. A two-factor-three-level split plot greenhouse experiment was conducted where the Fragaria × ananassa cv. Kaorino plants were subjected to full irrigation (FI) or deficit irrigation (DI), and within each irrigation regime the plants were subjected to no silicon application (N), silicon foliar application (L) or silicon root application (R), resulting in 6 treatments in total, viz., FIN, FIL, FIR, DIN, FIL and DIR. The results showed that DI increased the fruit sugars and anthocyanins concentrations without reducing the fruit size. Compared to foliar application, silicon root application was more favorable for fruit quality improvement, especially under full irrigation, by which the anthocyanins, ascorbate and glutamate concentration were significantly increased. Under deficit irrigation, silicon root application also altered the leaf photosynthetic pigments composition, increasing carotenoids and reducing membrane peroxidation to protect the photosynthetic complexes. Also, only when plants were under deficit irrigation, the silicon foliar application could perform better on the improvement of antioxidant capacity and nitrogen assimilation, enhancing the ROS scavenging and amino acids synthesis. Collectively, exogenous silicon application is promising in alleviating the negative effects of DI on fruit yield while improving fruit quality of strawberry.