Purpose: This study was undertaken to evaluate the effect of Nd:YAP laser on root surface cementum. Materials and Methods: Eighteen teeth extracted for orthodontic purposes were utilized in the study. Root surfaces were subjected to Nd:YAP laser using nine parameter settings pre-adjusted by the manufacturer to produce different energy density levels. Two teeth were subjected to each power setting at a fixed distance of 5 mm. After laser application, teeth were dehydrated and prepared for examination with a scanning electron microscope (SEM). Results: Changes in cementum surface were correlated to three ranges of energy density levels. With the energy density range from 509 to 573 J/cm², a heavily cracked cementum surface was the characteristic feature. With an energy density range of 796 to 892 J/cm², cementum depressions and perforations were observed with rough irregular margins denoting cementum destruction. Higher energy density levels ranging from 1051 to 1146 J/cm² affected the cementum severely, causing melting and cracking, exposing the underlying structures. Conclusions: It can be concluded from this study that Nd:YAP laser is destructive to root cementum and the extent of damage depends on the energy density level produced. Further studies are recommended to determine specific Nd:YAP laser parameters that will not adversely affect root surface cementum.