Polyamines are low molecular weight amines, with versatile and essential functions during the lifespan of prokaryotes and eukaryotes. Modulation of polyamine metabolism under biotic stress has attracted a great deal of interest; however, the precise functions of these amines in plant defence responses to pathogen attack are still poorly understood. Herein we summarise and review important aspects of the regulation of polyamine biosynthesis, catabolism and conjugation under biotic stress that might contribute to improve present‐day knowledge about these compounds in plant immunity. Particular attention is paid to the intracellular localisation of the proteins/enzymes associated to polyamine metabolism, as well as the impact of pathogen effector proteins on the control of plant polyamine metabolism is discussed.