Derivational morphemes pose problems for learners of English. In this connection, the nature of the problems faced by the learners needs to be investigated. The present study investigates the acquisition of English derivational morphemes by undergraduate level students. Data for the study was selected from four universities of KPK including Hazara University, Islamia College University, Kohat University of Science and Technology and Swat University. The findings of the study highlight that the problems faced by learners are different in nature. Some students did not easily acquire the English derivational morphemes. Their scores were different for different derivational morphemes suggesting that they had acquired some of these morphemes easily as compared to others. Derivational morphemes such as de-adjective nominal suffixes are acquired more easily as compared to de-verbal nominals. Our first hypothesis that states that class preserving suffixes are acquired easily than class changing suffixes was approved. Furthermore, the classes preserving derivational prefixes were found to be easily acquired than class changing derivational suffixes.