Objective: This paper discusses how service design is related to two well-known disciplines, interaction design and cognitive systems engineering, which are applied to the design of software, websites and mobile phones, and the design of control room of nuclear power plants and cockpit control, respectively. Background: Service design has been spotlighted recently due to its promisingness to service industry. Successful cases of service design are widely shared among designers. Service design, however, is treated as practice rather than a discipline. Method: It was discussed that it is important to consider the interaction between customers and services as in interaction design, and some domains are complex enough and have functional limitation as in cognitive systems engineering. Results: Models and design tools of the disciplines are introduced and applied to service design practices. Conclusion: It was concluded that service design has the characteristics of both interaction design and cognitive systems engineering.