Nucleolus is a non-membrane organelle found inside the nucleus. It is generally classified as nuclear subdomain that assembles ribosomal subunits in eukaryotic cells. They are responsible for the organization of the regions of the chromosomes that will further undergo different processes. Nucleolus is inside the nucleus of every eukaryotic which classifies the plants and animal cells. Therefore we can conclude that nucleolus is both present in animal and plant cells. 

If you are in detail of their comparison, plant cells have nucleolar vacuole which is not present in animal cells; and in general, plant cells contain more iron in the nucleolus than that of the animal cells.