Based on self-determination theory (Deci & Ryan, 2000), this study aims to verify how integrated regulation contributes to physical activity (PA) maintenance through promoting consistency in PA behavior, which is defined as the overall number of weeks during which participants reported sustaining the weekly frequency of their PA behavior. A 2-wave prospective design was used, and 824 adults (689 or 83.6% women, M age = 35.54, SD = 11.51) participated in the study. At baseline, participants completed the Behavioral Regulation in Exercise Questionnaire-2 (Markland & Tobin, 2004), an integrated regulation scale (McLachlan, Spray, & Hagger, 2011), and a questionnaire assessing the weekly frequency of their PA behavior (Godin & Shephard, 1985). Three months later, weekly frequency of PA behavior was reevaluated, and participants indicated the number of weeks during which they had maintained this PA frequency over the last 3 months. The results of a path analysis showed that: 1) integrated regulation was the only form of motivation related to PA behavior consistency and PA maintenance—independent of the initial PA level—over a 3-month period and 2) engaging in PA more consistently over the past 3 months was a significant mediator in the relationship between integrated regulation and PA maintenance. These findings illustrate that, compared to individuals who mainly practice PA for intrinsic or identified motivations, those who sustain PA practice because this behavior is congruent with their sense of self, thereby regulating for integrated reasons, have a greater chance of maintaining PA practice over time.