Social influence on technology acceptance behavior has been acknowledged but needs to be further articulated. While Subjective Norm (SN) has been dominantly used to capture the essence of social influence, the findings to date has led some researchers to question whether it captures the full extent of social influence. Recently, social psychologists have examined Self-Identity as a construct reflecting social influence on behavior. In particular, Self-Identity has been shown to have significant influence on voluntary behavior and have enduring effects, situations where the Subjective Norm had little effect. This study examines the effect of Self-Identity on technology acceptance decision in the context of a web-based class support system under the Technology Acceptance Model (TAM). The result demonstrates a significant direct and indirect effect of Self-Identity on technology acceptance. The result also confirms that Self-Identity has significant direct effect on the acceptance in voluntary and experienced situations, while Subjective Norm has no significant effect in both situations. Key implications for theory and practice are discussed.