Klaić was one of the most prominent Croatian and Yugoslavian medievalist in the 20th century. Some of her achievements are the innovative and modern approach to Croatian history (especially for the Middle Ages), which helped release it from the romantic nationalism of the 19th century, and the revaluation of older historical sources. However, a substantial portion of her views and conclusions are controversial and the work provoked strong reactions in historiography. For example, that the document Pacta conventa is a forgery probably made in the 14th century, her "lack of opinion" over the matter of 1102 in a 1959 article disputing Croatian writer Oleg Mandić's earlier work on the matter, and her view on the Croatian migration and old homeland in the 7th century, as well other topics of the early Croatian history.