Using an integrated CSR communication perspective, this chapter examines the role of internal CSR communication in achieving a successful, participative CSR approach. The special characteristics of CSR communication in general, and the distinctive challenges of internal CSR communication in particular, are identified. This allows a focus on and discussion of the challenges of the attitude-behavior gap regarding sustainable behavior in the work context. This perspective produces findings for how best to develop effective internal CSR communication that narrows the attitude-behavior gap. First, employees’ attitudes towards sustainability and the consequences for communication strategies that aim at changing these employee attitudes are discussed. Second, we investigate to what extent subjective norms and perceived behavioral control influence sustainable behavior at the workplace, in addition to the influence of attitudes toward sustainability and CSR. These discussions outline that every company has its own CSR specific environment and CSR specific organizational conditions for developing an effective, internal CSR approach. This chapter, however, identifies important antecedents and characteristics, which should be taken into consideration for an effective, internal CSR communication.