Receiving a constructive, supportive response from romantic partners after sharing good news has been shown to magnify the positivity of events and predict healthy relationship outcomes. We conducted a laboratory social interaction to determine whether supportive responses to success led to changes in facial expressions, sympathetic arousal, and felt emotions. Our methodology allowed us to break down the sequence of capitalization support. In 69 romantic couples, we recorded emotional processing before, during, and after the task in both partners. Person A received performance feedback on a computer task and shared their success via text messages with Person B, who then reacted to this success. Supportive capitalization responses led to greater felt positive emotions and a trend for fewer negative emotions; effects were similar for givers and receivers of supportive responses. Facial expressions were also happier for people receiving supportive capitalization responses. Results suggest the importance of addressing the giving and receiving of capitalization support within the same social situation.