The supervisor’s negative attitude towards voice and unavailability of communication channels are considered significant predictors of defensive silence. However, lesser consideration has been given to provide an in-depth explanation of how and why these motivational forces influence employees’ step by step conscious decision to engage in defensive silence. This qualitative study incorporates semi-structured interviews with bank employees of Khyber Pakhtunkhwa, Pakistan. Thematic coding and causal networking techniques were used to transcribe and analyse data and derive emerging themes. Taking influence from the elements of Expectancy Theory, this paper extends theory in the context of service sector by presenting two expectancy theory based defensive silence models. The first model provides reasons such as favoritism, political appointment, supervisor’s self-interest etc., to explain how and why the supervisor’s negative attitude towards voice influences employees’ cognitive mechanism to adopt defensive silence. Similarly, the second model presents the emerging themes like centralized decision system, career ladder, leg pulling, professional jealousy etc., to explain how and why unavailability of communication channels predicts defensive silence. Thus, the study extends the application of expectancy theory and defensive silence phenomenon to new empirical context. The paper concludes with a discussion on implications and recommendations for future work. Keywords: Defensive Silence; Supervisor’s Negative Attitude Towards Voice; Unavailability of Communication Channels.