The main objective of the present work was to numerically study the effect of loading conditions on the progressive damage of initial defects in steel pipelines. The adhesively-bonded composite sleeve repair technique was utilized to extend the lifetime of such cracked pipelines with different inclination angles (θ) under combined loads (i.e., internal and axial pressure) with different values. Three different glass fiber-reinforced polymer sleeves (GFRPs; [0°]8s, [90°]8s, and [0°/90°]4s) were simulated to study the effect of fiber orientation on the efficiency of composite sleeves in reducing the crack driving force. A three-dimensional (3D) elastic-plastic finite element method was utilized in the present study. The numerical results showed that the loading sequence has a great effect on the development of the crack-tip plastic zone size when the internal pressure is applied first. In the following two cases, if the internal pressure and the tensile stress were applied simultaneously or the tensile stress was applied in the first step followed by internal pressure, the loading sequence has little effect. In the case of the presence of internal pressure, the crack path is mainly dependent on it, and axial pressure has a marginal effect on its value. In such cases, applying [0°]8s sleeves is the best way to arrest cracks in steel pipelines. However, in the absence of pressure within the pipelines, [90°]8s sleeves are the appropriate ones to use to arrest the cracks due to axial pressure. Therefore, [0°/90°]4s sleeves may be recommended for repairing cracked steel pipelines to prevent crack growth in both situations.