An experimental investigation has been conducted to examine the enhancement of toughness of composites due to crack bridging under creep and fatigue conditions. The model composite used for the study consists of a metal wire inside a thick-walled glass tube. It is found that the fatigue and the creep resistance of the constrained wire depends upon the failure mechanism. Compared with the unconstrained monolithic wire, the model composite shows greater fatigue and creep strengths due to plastic constraint. The failure stretch of the constrained wire is less for fatigue loading than for monotonic loading; the contribution to toughening is thus reduced under cyclic loading. The failure stretch in creep is dependent only upon the failure mechanism and not upon the applied stress level.