To prevent damage to houses, we investigated the particular size and shape of gap that 12 masked palm civets (six subadults and six adults weighing 2.2–3.4 kg) could enter. After the animals were humanely killed, we measured the body parts of civets and compared those of animals that could and could not enter the gaps. The minimum sizes for different shapes of gaps that masked palm civets could enter were the H6 × W20 cm horizontally long rectangle, H20 × W6 cm vertically long rectangle, 8 cm square, and 9 cm diameter circle. There were no significant differences in most body parts sizes between individuals that went through the minimum-size rectangular gaps and individuals that did not. In contrast, differences in the sizes of body parts affected the minimum sizes of square and circular gaps that they entered. The minimum sizes of square and circular gaps that they entered could be predicted by the regression line of their body weight (square: y = 0.98x 5.75, r² = 0.76, P < 0.01, circle: y = 0.93x 6.84, r² = 0.72, P < 0.01).