Background: Job satisfaction is a key factor in organizational growth and success. Intern satisfaction, on the contrary, has not received much attention, despite its effect on all relevant players. Purpose: The purpose of this study is to examine factors affecting intern satisfaction in startup companies through the lens of the Job Characteristics Model (JCM) and additional work environment characteristics. Methodology/Approach: A total of 434 undergraduate students--participating in an unpaid internship for 10 weeks--filled out a 20-item survey regarding their experience. Items were designed to measure core job characteristics, the consequent experienced psychological states, work environment characteristics, and participants' satisfaction. Findings/Conclusions: Factors affecting intern satisfaction corresponded to predictions of the JCM as evidenced by three mediation models. Core job characteristics predicted hypothesized psychological states, which then predicted intern satisfaction. Learning opportunities, supervisor support, and organizational atmosphere contributed significantly in explaining additional satisfaction variance. Implications: Internship programs in startups potentially benefit all sides: students, institutions, and companies. In coordinating and planning these programs, both the universities and the companies would do best to consider the psychological factors that best predict the intern's satisfaction--feelings of responsibility, meaning, and knowledge of work results--in addition to offering learning opportunities, supervisory support, and a positive organizational atmosphere.