The objective of this study was to document how clinical dietitians working at tertiary hospitals spend their time based on several categories of activities using a time measurement study. The questionnaires were distributed to 14 tertiary hospitals, and dietitians answered by classifying their work activities into several categories such as general care, indirect care, direct care, outpatient care, and food service management. A total of 129 clinical dietitians replied and their answers were analyzed according to the categories of activities. The times spent on the categories are as follows: general care (76.7 mins/day, 14%), indirect care (228.4 mins/day, 35%), direct care (120.1 mins/day, 22%), outpatient care (61.5 mins/day, 11%), and food service management (99.0 mins/day, 18%). The total working hours for dietitians was 590.0 mins, which exceeds the standard working hours of 540.0 mins (9 hrs) a day. From this study, we found that clinical dietitians spent very limited time on direct care. Times spent on activities were different according to type of employment and food service. Internship dietitians spent their more time on general care (P<0.001) while irregular dietitians spent more time on outpatient care (P<0.05). In contracted managed food service hospitals, clinical dietitians spent significantly less time on food service management (P<0.001). Regardless of doctors' order and consultation fees, clinical dietitians performed more than 95 percent of free consultation to patients. Entry-level knowledge and skills of dietitians working at hospitals are very important for quality service, but it is equally important to create an administrative and social environment that encourages clinical dietitian to spend more time on direct patient care.