Rodolfo Lenz (1863–1938) left Germany late in the 19th century to settle in Santiago de Chile, where both taught linguistics and philplogy. The influence he exerted was very important, as he was largely responsible for the spreading the teachings of the German school of Philology in South America. Both historical linguistics and synchronic and dialectological studies advanced during this period, in Chile as well as in the rest of Latin America, as a result of his work. This paper analyzes Lenz’s grammatical and lexical contribution to Spanish, particularly through his seminal works La oration y sus partes (1920) and the Diccionario etimológico de las voces chilenas derivadas de lenguas indigenas americanas (1905–1910). Thus the origins and development of Lenz’s main grammatical ideas are treated in connection with the first work, but his lexicographical work is also described and analyzed in order to discuss the main problems he faced in its compilation, problems that Lenz himself addressed in the Introduction he wrote to this work.