It is widely believed that language learning, like any other human learning, involves the tendency to make of errors. (See Dulay, Burt & Krashen, 1982) Learner errors are an indication of the cognitive processes they make use of in analyzing, interpreting, and reorganizing the input they receive from the target language. Hence, learner errors are considered an integral part of language learning/acquisition. Consequently, error analysis (EA) emerged with the understanding that learner errors provide useful insights into the underlying processes of second language (L2) acquisition. From this stance, the present study examines 30 writing samples of a group of undergraduates of the Faculty of Humanities & Social Sciences, University of Ruhuna, focusing on the morpho-syntactic errors made by them. The objective of the study is to find out the types of morpho-syntactic errors made by the university undergraduates in their classroom work and assignments and to provide a Generative Syntactic explanation for them. The preference for morpho-syntactic errors over other error types is due to the fact that, by far, most of the L2 learner errors fall into this category. The selection of the Generative Syntactic approach is determined by the dearth of error analysis studies that have used this particular approach. Data analysis is done by using 10 syntactic rules and explanations in different modules of the Government and Binding (GB) theory. It is revealed that most of the errors are related to the predicates and argument structure relations, movement in embedded “Wh” questions, pronoun reference, clausal complementation, and adjacency violations. The least number of errors are related to adverb use, person-number agreement (phi-feature agreement), coordination, verbs with clausal complements, and in the use of ‘that’ complementizer.