Fragmentation of tin cluster ions (Sn-x(+): x=4-20) in the low-energy collisions with a HOPG surface has been investigated by means of a tandem time of flight mass spectrometer for the incident energy range of 0-300 eV. At low incident energies, smaller clusters (xless than or equal to11) fragmented by the atom loss process, whereas larger clusters (x>11) decayed by fission. The favored fragmentation paths were similar to those for Si and Ge cluster ions. The results support the structural similarities among Si, Ge, and Sn clusters in the present size range. The low-energy fragmentation patterns were compared with those obtained from theoretical calculations using generalized gradient approximation (GGA) and the B3PW91 exchange-correlation functional. It has been found that the B3PW91 hybrid functional results are consistent with the experimental observations.