The National Library collection is being accumulated since the library's foundation in 1919. Over 7 million publications are stored in it. The collection consists of three distinctive parts: holdings of Lithuanian publications, the main stock and special collections. There are more than 4 million books, periodicals, serials, reference publications as well as manuscripts (70,000 plus items), microforms (about 103,000 items) audio and video documents (approximately 63,000 items), old and rare books (over 30,000), compact discs, official documents of the Republic of Lithuania, foreign states and international organizations.

In 1992 the National Library collection was enlarged with the National Printing Archive (2 174 574 items) of the former Lithuanian Book Chamber. The Archive comprises books, maps, art publications and serials published in Lithuania since as early as the 16th century. Besides Lithuanian publications it includes books printed in the territory of Lithuania since the 16th century in other languages: Latin, Polish, Russian, etc. Some of them are of extreme rarity - a sole or very few copies having survived. The Archive also embraces 112 unique Lithuanian books from the 18th-19th centuries and some 40 Lithuanian books of same period which are absent in other libraries of Lithuania.

The collection of manuscripts of the Rare Book and Manuscript Department holds 70,000 storage units. Autographis, historical acts, photographs and other documents (since 15th century to the present) make up 200 separate collections. The accession of manuscripts to the library began in 1919-20. The most substantial part of the collection comprises private archives of the 19th-20th century persons (Lithuanian writers, public figures, scholars, artists who had been living in Lithuania and abroad). The most distinguished among the collection in the Manuscript Department are 149 parchments (privileges of Grand Dukes of Lithuania and Kings of Poland, the Papal privileges, etc.). It is worth mentioning a collection of handwritten and multiplied small-size newspapers and the one of individual manuscripts containing notable 16th-20th century works in philosophy, literature and history.

In the Rare Book division of Rare Book and Manuscript Department there are 30,000 books dated from the 15th to 18th centuries. Edition of works by early Church reformers (Martin Luther, Philip Melanchton) and humanists (Erasmus of Rotterdam), the 17th-18th century dissertations and theses of higher schools of Europe, editions and commentaries by classical authors and similar works are of particular significance.

The amount of documents stored in the Music Department collection exceeds 200,000. It is composed of printed music, books, journals, audio and video documents. Some 100,000 items of printed music represent diverse musical styles and genres ranging from 16th century to the present. The Department houses more than 500 titles of rare music scores, a national printed music collection currently holding approximately 90% of all Lithuanian published material, is being permanently accumulated. A collection of records, compact discs, audio and video recordings numbering 55,000 exhibits production of 40 foreign recording companies ranging from the samples of Berliner's early disc to the modern releases in this field. The national audiovisual collection contains 7 thousand pieces (about 2 thousand titles) covering the period from 1907 up to nowadays.