The study investigated pre-service ICT teachers' perceptions of algorithm visualization (AV) with regard to appropriateness of teaching levels and contribution to learning and motivation. In order to achieve this aim, a qualitative case study was carried out. The participants consisted of 218 pre-service ICT teachers from four different universities. Data were obtained through an open-ended questionnaire (n = 210) and interviews (n = 8). The qualitative data were analyzed using content analysis techniques. The results indicated that about half of the pre-service teachers thought AV to be appropriate for use in elementary and middle schools. A smaller number of participants thought that using AV is appropriate in high schools and colleges. Almost all of the participants thought that AV effectively contributes to learning and teaching computer programming. Participants explained this effect in terms of seven properties of algorithm visualization environments: Visualization, Algorithmic Thinking, Enjoyable Learning, and Progressive Learning, Learning by Doing, Game-based Learning, and Scaffolding. Moreover, results showed that most of the pre-service ICT teachers believed that AV contributes effectively to motivation. They explained this positive contribution to motivation in terms of six properties of AV: Easy to use, Visual, Fun, Quick Produced, Active and Game-based.