Introduction Patient portals are online applications that allow patients to interact with healthcare organizations and information. Portal messages exchanged between patients and providers contain diverse types of communications, including delivery of medical care. The types of communications and complexity of medical decision-making in portal messages sent to surgeons has not been studied. Materials and Methods We obtained all message threads initiated by patients and exchanged with surgical providers through the Vanderbilt University Medical Center patient portal from June 1 to December 31, 2014. Five hundred randomly selected messages were manually analyzed by two research team members to determine the types of communication (i.e., informational, medical, logistical, or social), whether medical care was delivered, and complexity of medical decision-making as defined for outpatient billing in each message thread. Results 9,408 message threads were sent to 401 surgical providers during the study period. In the 500 threads selected for detailed analysis, 1,293 distinct issues were communicated, with an average of 2.6 issues per thread. Medical care was delivered in 453 message threads (90.6%). Of these, 339 (67.8%) of message threads contained medical decision-making. Overall complexity of medical decision-making was straightforward in 210 messages (62%), low in 102 messages (30%), and moderate in 27 messages (8%). No highly complex decisions were made over portal messaging. Conclusions Through patient portal messages, surgeons deliver substantial medical care with varied levels of medical complexity. Models for compensation of online care must be developed as consumer and surgeon adoption of these technologies increases.