The Twort-like bacteriophage 812 from the Myoviridae family is a promising therapeutic alternative for treatment of antibiotics-resistant bacterial infections. We previously reported high-resolution cryo-electron microscopy reconstructions of the isometric head and the double-layered tail of this phage [1]. The portal domain is located in the neck region at the interface between the head and the tail and serves as a channel for DNA translocation. In situ cryo-EM reconstruction of the portal complex from phages after genome release, obtained at 3.8 Å resolution, reveals that the portal adopts a dodecameric ring-shaped conformation with an outer diameter of 13 nm. A prominent crown composed of axially stacked C-terminal helices forms a funnel-like structure opening towards the head interior. In contrast, a preliminary 6.5 Å cryo-EM electron density map of a recombinant portal complex shows that the latter assembles predominantly into 13-meric structures with a diameter of 15 nm and presents conformational differences in the crown and the stem regions. These differences likely stem from mis-folding in solution in absence of phage chaperones, but they could also correspond to structural rearrangements experienced by the portal complex during different stages of phage maturation.