As a result of the coupling between the solar wind and the Earth’s magnetosphere-ionosphere system, plasma density irregularities are often developed in the polar ionosphere, which in turn can severely degrade satellite-based positioning and communication systems. High-latitude ionospheric irregularities are often associated with polar cap patches, blobs, particle precipitation, and the main ionospheric trough. These ionospheric phenomena can be studied by using in-situ data from polar orbiting satellites. Here, we present a statistical study based on observations from the European Space Agency’s Swarm mission. Swarm satellites are especially useful at high latitudes due to the good coverage in both hemispheres as compared to ground-based instruments. Two comprehensive datasets are used to detect ionospheric irregularities, i.e., electron density from the Langmuir probe and GPS TEC from the GPS receiver onboard Swarm satellites. We derive several parameters to describe ionospheric irregularities, e.g., the rate of change of density index (RODI) and electron density gradients (\nabla_Ne) from the electron density data, rate of change of TEC index (ROTI) from GPS data (these parameters are included in the Swarm IPIR product). The statistics show that electron density and plasma irregularities are modulated by the Earth’s magnetic field in both hemispheres. The climatology maps in magnetic coordinate show predominant plasma irregularities near the dayside cusp, polar cap, and nightside auroral oval. The spatial distribution of plasma irregularities are also modulated by the interplanetary magnetic field (IMF), e.g., when considering the IMF By component, the irregularity distribution in the cusp and polar cap shows asymmetry between the Northern (NH) and Southern hemispheres (SH), i.e., for negative IMF By, the irregularities are stronger in the dusk (dawn) sector in the NH (SH) and vice versa. This feature is consistent with high-latitude ionospheric convection pattern that is regulated by the IMF By. Plasma irregularities are also strongly controlled by solar activity within the current declining solar cycle. Ionospheric irregularities in polar caps show clear seasonal variation with higher values near equinoxes and lower values near solstices for both hemispheres.