Phenol–urea–formaldehyde (PUF) organic foams have been firstly synthesized from phenol–urea–formaldehyde resin under alkaline conditions. Carbonization and CO₂ activation were then used to prepare a novel monolithic nitrogen-containing activated carbon foam with both interconnected macroporous and micro/meso-porosity structures from the developed PUF organic foam. The macroporosity produced from the organic foams, which corresponds to the connected network of cells, has a diameter in the range of 100–600 μm. The micro/meso-porosity produced by activation is located at the inner surface of the cells. The developed carbons have achieved an apparent surface area as high as 1674 m² g⁻¹ and microporous volume as high as 0.86 cm³ g⁻¹, which are similar to that of many commercial carbonaceous adsorbents, but with a nitrogen content around 1.5 wt%. These activated carbon foams are expected to have higher adsorption kinetics and some special applications due to the heteroatom nitrogen introduced and the bimodal cellular structure.