The present invention relates generally to a protective helmet that includes a shell defining a shell exterior and a shell interior configured to protectively receive a wearer's head. The helmet also includes an internal support disposed in the shell interior in supportive association with the shell for supporting the shell on the wearer's head, and an adjustment member associated with the internal support for adjusting the size of the internal support to fit to the wearer's head. The adjustment member and the shell are configured and dimensioned such that the adjustment member is operable to adjust the internal support from outside the shell while the helmet is mounted on the wearer's head.