The relative growth of chela, abdomen, and male first pleopod is described forMacrophthalmus hirtipes(Jacquinot, 1853) (Brachyura: Ocypodidae) from the Avon‐Heathcote Estuary (43°33′S, 172°44′E) and from a marine inlet at Governors Bay (43°38′S, 172°39′E), Canterbury. Marine and estuarine crabs had a similar estimated size of maturity of between 10 and 13 mm carapace width. Coincident with sexual maturity was an acceleration in the growth rate of the male chela, an enlargement and change in shape of the female abdomen, and a change to negative allometric growth of the male first pleopod. Statistically significant (P < 0.05) intraspecific differences in some body proportions were found between the 2 populations. Relative growth of the chela ofM. hirtipesis similar to that of Australian macrophthal‐mids.