The aim of this study is to identify problems in the instruction process experienced by instructors teaching international students at English preparatory classes at tertiary level and their suggestions for the solution of the problems. To this end, data were obtained from 26 instructors, selected through criterion sampling, at the school of foreign languages at a state university to define problems experienced in the instruction of reading, writing, speaking and listening skills, the process of assessment and evaluation, classroom communication, behavior management and other related issues regarding international students. This is a qualitative and descriptive case study and a semi-structured interview form was used as data collection instrument, developed based on the research questions, consisting of six questions. The data were analyzed through descriptive analysis and reported with quotations. The research findings suggest that the highest number of problems are experienced in the issues of writing skill, speaking skill, assessment and evaluation, classroom management, reading skill and listening skill respectively. In addition, difference in the alphabet used, pronunciation problems, use of native tongue in lessons, problems in exam practices, discipline problems and absenteeism problems are mostly stated problem areas. Besides, the instructors also offered practical suggestions for the solution of the stated problems. It is expected that the results of the study will put forth the opinions of instructors at tertiary level who are significant stakeholders of the rapid internationalization process in higher education lately and who are also ignored in the literature and thereby contribute to development of practices in the field.