Hypothetical bias (HB) is barely discussed in the tactical-level pedestrian route choice problems since the models are hard to validate and compare across studies. This study explores the impact of choice scenario formatting (in numbers, diagrams, and pictures) on tactical-level pedestrian route choice within the choice experiment framework and discusses various sources of HB. I conducted two waves of paired SP-RP experiments in China, used three metrics to quantify HB, and tested the performance of six calibration methods (three developed from the cognitive science perspective, three from transportation literature) and their external validity. I also tracked participants’ perceptions of path attributes during the experiment. My findings suggest that (i) “crowdedness” is the key to understanding choice preference. (ii) Context has a significant impact on participants’ perception of path attributes. (iii) The diagram and the picture format produce more bias than the number format. (iv) Systematic HB exists. The format and the specific choice scenario design are the two major sources of HB. (v) Three calibration methods are effective: recoding uncertain choices to the status quo, incorporating personality scores, and incorporating thinking pattern scores. These findings demonstrate the great potential of understanding tactical-level route choice from a cognitive science perspective and emphasize the importance of experimental design.