This paper provides an overview of an analytical method to assess tubing loads, design integrity, and buckling behavior under complex mechanical, pressure, and thermal-loading conditions. The methodology uses a proven tubular design and stress analysis software, applied to a multi-zone intelligent completion and a dual string TAML level 5 multilateral well. Tubing load scenarios are evaluated in separate phases of the completion installation and operating phases. Simultaneous production and injection scenarios are also examined for a dual string multilateral well. Full well models are created and evaluated, analyzing stress-loading for both well types. Thermal simulation is first performed, followed by tubular stress modeling to guide tubular selection and completion design. Analysis covers completion operations during installation such as packer setting and testing, well operation scenarios such as well stimulation, simultaneous production / injection for the dual string multilateral, and production scenarios for the multi-zone intelligent completion with multi-position Interval Control Valves (ICVs) in various positions. Results presented show temperature/pressure changes for each simulated scenario and the corresponding load state cases in the modeled wells. Tubular axial loading, burst and collapse limitations, pipe movement and buckling potential are modeled. The resultant forces on completion packers are modeled for the well with the multi-zone intelligent completion. These results are evaluated to select and optimize the well completion design and also identify well operating limits with respect to a set of combined ICV positions during commingled well operations. Results on estimated annular pressure buildup during well operations are also presented with some guidelines on minimizing annular pressure buildup in annuli through mechanical control or well completion landing practices. This paper provides workflow outlines and results for tubing stress analysis in complex multi-zone intelligent completion and dual completion multilateral wells. Variations in operating temperatures and pressures in such scenarios can place completions in conditions that can exceed design margins that are already limited due to production-casing diameter constraints. The methods and results presented are useful for balancing design-versus-risk for the completion. They can also provide savings by optimizing well design to meet design integrity standards without being overdesigned.