Internet of things (IoT) applications require orientation insensitive wireless devices to maintain stable and reliable communication as well as the localization capability using the global positioning system (GPS). For those reasons, antennas providing near-isotropic radiation pattern with wide circular polarization (CP) coverage are high in demand for IoT applications. In this work, we derive conditions for 3D antenna-on-package (AoP), through a combination of three orthogonal dipoles model and particle swarm optimization (PSO) technique to achieve near isotropic radiation pattern and wide CP coverage simultaneously. Design guidelines have been provided, and a practical AoP has been designed on a 3D cube package by following this guideline. A prototype has been fabricated and the measured results demonstrate an isotropy of ~ 93% and CP coverage of ~18%, which matches well with the predicted results from the theoretical analysis as well as the full wave electromagnetic simulations.