Nickel-based superalloys are key materials for aerospace and gas turbine applications. Traditional manufacturing approaches struggle to produce controllable porous structures with complex topologies. This review focuses on additively manufactured porous Ni-based superalloys, and summarizes progress in porous structure design, including disordered, lattice, TPMS, bio-inspired, and AI-assisted structures. Common additive manufacturing technologies are introduced, along with their effects on microstructure evolution and defect formation. The review discusses non-equilibrium microstructures, elemental segregation, and typical defects such as lack-of-fusion, keyhole porosity, and residual stress, as well as their influences on strength, fatigue, and creep behavior. Post-processing strategies for defect mitigation and performance optimization are also summarized. This review highlights the unique mechanical and physical behavior of porous structures compared to bulk materials, with an emphasis on anisotropy, stress localization, and defect sensitivity. Finally, several critical and specific challenges are identified, including multi-scale modeling, microstructure control in complex topologies, fatigue prediction, and physics-constrained AI design. This review aims to provide a clear, focused, and structurally consistent overview of the current state of the field, and to support future research on additively manufactured porous Ni-based superalloys.