While multilingualism itself is a widely analyzed topic, a study about multilingualism at German schools abroad is so far unique. This quantitative study investigates the differences in the size of German expressive and receptive vocabulary between monolingual and multilingual students, aged between 5 and 11 years. A cohort of 65 multilingual students with diverse linguistic backgrounds recruited from a German school abroad in The Hague, The Netherlands, was compared to a group of 880 monolingual students at schools within Germany. To test the children's vocabulary size, the "Wortschatz- und Wortfindungstest für 6- bis 10-Jährige" developed by Glück was administered. The study revealed partly significantly lower scores in the expressive vocabulary test for the multilingual students, as hypothesized by the researchers and detected in previous studies examining the difference between populations of multilingual and monolingual speakers of one particular language. In the receptive vocabulary test, the multilingual and monolingual students' scores did not differ significantly, a result consistent with findings in similar studies.