An analytical method based upon a sublaminate modeling approach was developed to quantify the loss of the effective axial and bending stiffnesses due to defects in laminates. Defects considered were single and multiple delaminations as well as ply fiber waviness. Laminates with (45 °, −45 °, 0 °, 90 °, 0 °, 90 °)s layup of AS4/35016 graphite/epoxy were used to investigate the stiffness loss due ... [Show full abstract] to defects at various interfaces and with various percentages of overlap in the multiple delaminations.It was found that the reductions of the stiffness in a given direction is more pronounced if the thinner sublaminate of the delaminated laminate contains a ply which contributes more stiffness in that direction. For multiple delaminations, reduction of stiffness increases as the overlap percentage of two delaminations decreases. The loss of axial and bending stiffness is significant if a ply contributing more stiffness in the laminate contains a fiber waviness.