Malaysia has experienced a rise inforeign labor inflows in response to steady economicexpansion and demographic changes. The foreign workforce hasbeen hovering around 15 percent of the total labor force inrecent years according to Labour Force Surveys by theDepartment of Statistics Malaysia (DOSM). Foreign labor isconcentrated in low-skilled occupations, and in Malaysia theterm “foreign worker” specifically implies a foreigner doinglow-skilled work. These foreign workers come fromneighboring countries, predominantly Indonesia, Bangladesh,Nepal and the Philippines. This report is one of the firstattempts, to team’s knowledge, to estimate the number ofirregular foreign workers in Malaysia. Its contributions tothis field are the following: first, it develops aconceptual framework that lays out potential entry points ofirregular foreign workers. Second, it identifies alternativeadministrative data sources that could help estimate themagnitude of irregular foreign workers at each entry point.Third, it identifies methods that can be employed to measureirregular foreign workers with the current data availabilityand outlines what can be carried out further in the futureusing Immigration Department’s microdata. This reportestimates the total number of foreign workers inMalaysiaranged from 2.96 million to 3.26 million in 2017.Among these, the number of irregular foreign workers isestimated to be 1.23 million – 1.46 million.