Many studies have reported success with respect to tagging crabs purpose of population and home range studies (McConaugha, 1995; et al., 1998; Chen & Kennelly, 1999; Diaz & Conde, 1999; Brousseau Gonzalez-Gurriarán et al., 2002; McGarvey et al., 2002; Maitland et Few studies, however, clearly outline exact methods and materials used other researchers can replicate the tagging technique. The purpose of to describe a technique for tagging small crabs individually, so that followed for field studies. 'Aratus pisonii' (H. Milne Edwards, 1837) is a small, scansorial grapsid inhabiting Atlantic and Pacific shores from Florida to Brazil and Mexico respectively. Males and females attain a maximum size of 26 mm carapace and breed throughout the year (Warner, 1967). Being a small, agile tree-crab, 'A. pisonii' do not make easy subjects for marking or observing for studies.