Internal browning is a physiological disorder affecting tomatoes (Solanum lycopersicum L.), and presents a major problem to Japanese producers. Internal browning is characterized by the discoloration (browning) of the inside of fruits while the external surface appears normal; consequently, affected fruits reach consumers without detection. Internal browning may be caused by Ca deficiency and may be suppressed by performing defoliation. We investigated the effect of defoliation on the occurrence of internal browning in Momotaro York tomatoes planted hydroponically in a glass greenhouse and in a controlled environment chamber. The occurrence of internal browning was significantly lower in the fruits of defoliated plants (50% of leaf area removed) than in the control plants (no defoliation). Moreover, the Ca content in the water fraction of young fruits obtained from defoliated plants was significantly higher than that in control plants. Overall, this study demonstrates that defoliation increases the Ca content in fruits and reduces the occurrence of internal browning in tomato plants.