The use of fitness apps is very valuable for fitness centers, as members tend to stay involved for longer, increasing loyalty to the fitness center. The objective of the study is to determine use behavior (UB) and behavioral intentions (BI) to use the fitness apps in fitness centers and to analyze whether there were significant differences between customer’s profile. In addition, to analyze whether BI influences UB with the app. The sample included 1.338 members from Portuguese fitness centers. The UTAUT2 served as base model. JASP software was used for data analysis. A descriptive analysis of participants, exploratory factorial analysis, reliability analysis, one-factor ANOVA, and linear regressions were performed. The descriptive analysis indicates the profile of members using the application. It is women, members with higher academic qualifications, those who frequently attend the fitness center, and those who have been members for two or more years who use the app the most. Also, the results showed that UB was positively correlated with BI. Therefore, it is suggested that fitness centers invest in the use of an app, since their use is also related to customer retention that can lead to loyalty, which benefits the organizations.