In this Letter, Young’s double-slit experiment with vector vortex beams is investigated. We present the results for various Poincaré–Hopf index beams of this class considering all four major types. Polarization associated morphological changes in the far-field interference pattern are studied both theoretically and experimentally. The Fraunhofer pattern consists of lattices of polarization singularities of the generic type, located on a line, in a direction perpendicular to the slit. The number of linear lattices varies as a function of Poincaré–Hopf index
η
of the beam that is diffracted, and the number of intensity nulls occurring along the vertical line is equal to
|
η
|
.