An investigation was conducted to determine the cause of weld cracking in laser Be/Al weldments. In agreement with earlier studies, features consistent with hot shortness cracking on the fracture surfaces were observed. Closer examinations of the fusion zone crack regions reveal that the cracking was a result of thermal stress, shape of weld roots and impurities segregation. The defects are related to the weld parameters. The cracks easily nucleate at conduction mode weld and blowholes easily appear at keyhole mode weld.