Jonschwil has a population (as of ) of . , about 9.4% of the population was made up of foreign nationals. Of the foreign population, (), 31 are from Germany, 31 are from Italy, 150 are from ex-Yugoslavia, 21 are from Austria, 15 are from Turkey, and 27 are from another country. Over the last 10 years the population has grown at a rate of 11.1%. Most of the population () speaks German (94.9%), with Albanian being second most common ( 1.7%) and Serbo-Croatian being third ( 1.1%). Of the Swiss national languages (), 2,974 speak German, 6 people speak French, 24 people speak Italian, and 1 person speaks Romansh.