Weight and other body measurements of crested porcupines captured in the Maremma Natural Park, central Italy, were compared between the sexes. The weights and body lengths of females were significantly greater than those of males (P < 0.05). A stepwise discriminant analysis showed that 802 of the females (N = 10) and 85.7% of the males (N = 14) were classified correctly by the discriminant function, which was correlated most highly with body length and weight. Body length proved the best single variable for differentiating between the sexes. The larger size of females is discussed in relation to the reproductive and life‐history strategies of the crested porcupine. The distribution and quality of food resources is suggested as the factor responsible for the evolution of sexual size dimorphism in favour of females in the crested porcupine.