Synopsis The book 'Ferns of Nainital' deals with account of taxonomy and ecology of ferns of Naini Tal ranging from 600 - 2611 m. It is based on the extensive collections made periodically in different localities of Naini Tal. The present work records 135 species, 6 varieties and 2 forma belonging to 49 genera and 25 families. The families and genera are arranged according to Mehra's system of classification. Nomenclature has been updated with the help of available literature. Besides this observations on the habit, habitats, size of fronds, nature of rhizomes, abundance and ecology of various species of ferns were also made.