Existing research on designers mostly focuses on the specific activities they undertake during the design process, such as brainstorming, sketching, and prototyping. This research examines how designers utilize their personal experiences in real-life interaction design practices and aims to bring attention to the value of designers’ judgments and interpretations. Designers’ personal experiences refer to the collections of their individual experiences derived from their direct observation or participation in past real-life events and activities, as well as their interaction with design artifacts and systems (whether digital or not) in professional and personal contexts. In our main study we conducted a multiple case study that looks at how interaction designers worked with their personal experiences in three industrial interaction design projects, thus calling for the need to explicitly recognize the legitimacy of using and better support of the use of designers’ personal experiences in interaction design practice. In earlier research, we proposed and experimented with a design technique we referred to as memory-storming, to investigate how design insights and concepts can emerge through externalizing, sharing, and analyzing designers’ personal experiences.