The literature has shown that emotions felt during collaboration can be different from those displayed to the partners. Emotions can be expressed to influence others, or masked for self-protective, pro-social or task management purposes (Cahour, 2013). In this study, we compared emotions expressed during a computer-mediated collaborative task versus emotions reported while participants watched the video of the collaboration. We also investigated whether the display of emotion was related to emotion regulation strategies; in particular, we studied individuals' tendency to either inhibit the expression of emotions (suppression), or reinterpret the situation so as to modify the resulting emotional impact (reappraisal; Gross & John, 2003). Participants of this study collaborated remotely in dyads, and built together a violence prevention slogan. They were asked to (orally) debate and organize their ideas using voice-conferencing and argumentation graph tools. Half of the dyads were provided with an emotion awareness tool (EAT), which gave members the possibility to 1) communicate their emotions to their partner using a predefined list of 10 positive and 10 negative emotions and 2) visualize their partner's emotions throughout the interaction. After collaboration, they completed the Emotion Regulation Questionnaire (Gross & John, 2003). They were then provided with a video of their group work, and were asked to annotate moments when they felt an emotion (debriefing). Results showed that the percentage of negative emotions expressed via the EAT (14% against 86% for positive emotions) was lower than the percentage of negative emotions reported during the debriefing (28.7% against 71.3% for positive emotions) (p < .001). Moreover, the difference in percentage between expressed and reported negative emotions was positively related to the participants' tendency to use the reappraisal strategy (r = +0.5, p < .05), and not related to their tendency to use the suppression strategy (r = -0.01, p > .05). Thus, the small number of negative emotions communicated during collaboration would not be due to a strategy of masking their emotional expression. It would be rather explained by the participants' tendency to modify their interpretation of the situation so as to prevent the potential negative impact of some emotional events on group work.