This study uses an innovative tourism product development approach, based on co-creation or customer involvement, related to Lake Balaton, a mass tourism-based destination in Hungary, from the point of view of the market segment of active cycling tourists. The investigation of opportunities for the development of cycling tourism first of all relies on the new approach of attraction and product development around the destination, in which it is important to take into consideration the consumer preferences of the most important related group of tourists—active cycling tourists. The sustainable approach of tourism product development also provides an opportunity to decrease the spatial and temporal concentration of tourism, which is largely concentrated on the summertime season. The aim of this study is to explore aspects of the customers’ demand for tourism development in terms of cycling tourism with the help of primary data collection, in order to provide adequate directions for sustainable tourism development in the destination. Revealing the demand side of active cycling tourism related to Lake Balaton, the authors used both qualitative (focus group discussions and structured interviews) and quantitative questionnaire survey (computer-assisted data collection) research methods. The latter online surveys were carried out in November and December, 2019, and resulted with an appraisable sample of 809 questionnaires. As for the method, descriptive statistics and relationship analyses were applied. More than five thousand (5050) possible relationships were examined between the closed answers of the questionnaire by Kendall's rank correlation coefficient (τ) and Cramer’s V, depending on whether they could be measured on a nominal or ordinal scale. The results show that the content analysis of the primary research provides well determined directions for the sustainable tourism development of cycling tourism at Lake Balaton, so customer involvement seems to be a win-win situation both for the customers (tourists) and the decision makers.