Multilingualism and multiculturalism have become major preoccupations for Library and Information Science (LIS) which has to be as fair as possible to ensure and sustain knowledge diversity as a driver for development. This paper offers a broad overview of multilingualism and multiculturalism embedding into Digital Libraries (DL). We survey studies written in English over the past two decades (from 2002 to 2022) and indexed in one or more of the following databases: Science Direct, Google Scholars, Taylor and Francis, and Emerald Insight. We summarized studies to offer insights and outline opportunities in this area and classify them into five research themes: (i) studies describing Cross-Language Information Retrieval (CLIR) in Digital Libraires, (ii) studies describing building, enriching and using multilingual resources in digital libraries (iii) studies focusing on multilingual digital libraries initiatives, (iv) studies on collaboration, minority languages and ethics issues in digital libraries, and (v) studies on multilingual user needs. This survey aims to identify, collect and categorize the research literature on multilingualism and multiculturalism efforts in Digital Libraries.