Rapeseed meal (RSM) is an important plant protein source for animal feeding, but its nutritional value is influenced by cultivar, dehulling and processing, while glucosinolates, phytic acid and fibre can limit its utilization in animal diets. This review synthesizes peer-reviewed studies from an animal nutrition and feed science perspective to examine the reported variation in RSM composition and the effects of solid-state fermentation (SSF) on its feeding value. Across the reviewed studies, crude protein (CP) ranged from 31.8% to 42.5%, glucosinolates from 15.5 to 75.6 µmol/g, phytic acid from 2.66% to 5.24%, and neutral detergent fibre (NDF) from 23.9% to 47.1%. These differences illustrate the influence of raw material characteristics and processing on the nutritional attributes of RSM. SSF using microorganisms belonging to Bacillus, Lactobacillus, Saccharomyces and Aspergillus reduced glucosinolates, phytic acid and fibre while generally increasing CP and peptide concentrations. The magnitude of these changes varied considerably among microorganisms and fermentation conditions. The reviewed evidence indicates that SSF is not simply a method for reducing individual anti-nutritional factors; it can simultaneously modify several characteristics that determine the nutritional usefulness of RSM. These changes make SSF a promising approach for upgrading RSM as an animal feed ingredient.