Santillana has always been a firm believer in the idea that a good education requires a library where students can expand their knowledge acquired from textbooks (classroom books), and teachers can update their skills in teaching, methodology or psychology. Therefore, educational reference books have played an important role in Santillana's publishing activities.

Currently, the publication of reference works offers a wide range of materials to complement the textbooks designed for each educational level (preschool, primary school and secondary school) for the students of different Spanish speaking countries.

Within the range of reference books, two basic sections stand out: Lexicography and Cartography; School Dictionaries and Reference.

This section covers dictionaries, encyclopaedias and atlases, with specific publications for different countries and autonomous regions in Spain. These reference books have been specially adapted for schools, as can be seen by the numerous editions of the Nuevo diccionario esencial and the Nuevo diccionario escolar de la lengua española. It also includes dictionaries for the general public, such as Diccionario de sinónimos y antónimos, and the collection of dictionaries started in 1999 by Manuel Seco, a member of the Spanish Academy, published under the Aguilar Dictionaries imprint.

Towards the end of 1999, Grupo Santillana published a specialized dictionary which many consider is the most important lexicographical work in recent decades: Diccionario del español actual, edited by Manuel Seco. This is the first Spanish dictionary that registers the living language of the second half of the twentieth century with authentic example sentences of written Spanish usage for each headword and entry.

In 2000, the Diccionario abreviado del español actual was published which is based on the same databank as the abovementioned dictionary, and in the autumn of 2004, the Diccionario fraseológico documentado del español actual appeared. It contains more than 16,000 phrases of current Spanish usage, with authentic model sentences of the written language and notes on grammar and usage.

Santillana Reference has developed a series of books which can be used in the classroom and at home as supplementary materials for the textbook, and whose main aim is revision and knowledge reinforcement.

It should be emphasized that in this series there are two grammar books, adapted for primary and secondary schools respectively (Gramática y Ortografía para Primaria y Gramática y Ortografía para la ESO) as well as the Esenciales series, which cover the basic concepts of the key subjects at each stage (Esencial for Primary school) or year (Esencial for 1st year of secondary school, Esencial for 3rd year of secondary education). All the concepts are dealt with in a very precise and organized way, which make them ideal for revision.