This chapter provides a comprehensive evaluation of well integrity challenges specific to unconventional resource development, particularly in shale gas and tight oil plays. The unconventional landscape is marked by long horizontal laterals, multi-stage hydraulic fracturing, and high-density well pads, introducing unique mechanical, thermal, and operational stresses on wellbore systems. The chapter explores the integrity risks posed by repeated high-pressure cyclic loading during fracturing, including casing fatigue, cement debonding, and annular micro-annuli formation, supported by numerical simulations and case studies. It details advanced mechanical models that quantify stress distributions in casing and cement, and presents fracture propagation equations to assess induced pressure effects. Special attention is given to cement sheath performance in horizontal wells, where suboptimal centralization, fluid migration, and thermal cycling pose severe threats to zonal isolation. The design of fracture-resistant and thermally stable cement systems, combined with robust placement techniques and verification methods (e.g., ultrasonic logs, CT imaging), is emphasized as critical for maintaining integrity throughout the well lifecycle. Fracture height containment is addressed through geomechanical modeling, real-time monitoring, and tailored stimulation design to prevent out-of-zone fracture growth, especially toward aquifers. The chapter also discusses long-term integrity threats such as corrosion, casing deformation, and parent–child well interference, all of which can compromise structural barriers if unmitigated. Finally, it outlines abandonment strategies for multi-stage horizontal wells, highlighting the complexity of ensuring permanent isolation in deviated sections. By integrating engineering models, operational practices, and field insights, this chapter provides a framework for adapting conventional well integrity principles to the demanding environment of unconventional resource development.