The aims of the present study are to explore wrong English collocations made by some Indonesian English learners and to find out the causes of the wrong collocations. Twenty seven wrong English lexical collocations and nine wrong grammatical collocations collected from the students’ translation and writing assignments have been examined. After comparing the patterns of English collocations and the Indonesian collocations it is found out that the erroneous English collocations are attributed to four causes: (1) learners’ lack of knowledge of collocation, (2) differences of collocations between English and Bahasa Indonesia, (3) learners’ low mastery of vocabulary and (4) strong interferences of the learners’ native language.It is suggested that the students should be informed that collocation, like grammar, is one aspect of not only English but all other languages that should be learnt if they want their English sound natural and mastery of vocabulary can contribute to the constructing of correct collocations.