Axial compression experiments were conducted on pultruded E-glass fiber-reinforced polymer laminates of different slenderness. Second-order deformations greatly increased the bending moments and shear forces of slender specimens. Delamination failure occurred in all specimens, independent of slenderness. Based on measurements of lateral deformations at delamination initiation, the distribution of shear forces was determined and the stress state at failure was obtained and compared to an adopted failure criterion. Ultimate loads were further predicted based on FE analysis. After delamination, specimens could sustain a residual load, which could be estimated based on a buckling analysis on the separated laminates for specific cases.