Background: Self-efficacy (SE) is one factor which contributes to successful hearing aid (HA) outcomes. This study investigated new and experienced HA users HA-SE over a 12-week interval post-HA fitting, using satisfaction with HAs and hours of use as outcome measures. The current study aimed to investigate 3 questions: 1) What is the pattern of HA-SE over the trial period and are there significant differences between new and experienced HA owners? 2) Does HA-SE at the various assessment points predict satisfaction with HAs for new or experienced HA owners? 3) Does HA-SE at the various assessment point predict HA use for new or experienced HA owners? Method: This research employed a longitudinal intervention study design. New (n = 80) and experienced (n = 113) adult HA users were recruited from a private HA clinic Phoenix, Arizona, USA. Participants completed the Measure of Audiologic Rehabilitation Self-Efficacy for Hearing Aids (MARS-HA; West & Smith, 2007) at 4 stages through the fitting process: immediately following the HA fitting, 1 week post-fitting, 4 to 6 weeks post-fitting and 12 weeks post-fitting. Information was also collected on age, gender, hearing handicap, hearing impairment, number of appointments attended, average hours of use, and cost of the hearing aid to the participant. Hours of use was measured via data logging and self-report at 4 to 6 weeks post fitting and satisfaction was measured at 12 weeks post-fitting using the Satisfaction with Amplification in Daily Life questionnaire (SADL; Cox & Alexander, 1999). Results: There was little evidence to support a difference between HA-SE for new and experienced HA users, so the groups were combined for the remaining analyses. HA-SE significantly improved over the 12-week interval, although some subscales still showed a low proportion of users with adequate HA-SE at the end of the 12 weeks. Various MARS-HA scores entered into regression equations to predict SADL scores at 12-weeks, although hours of use at 4 to 6 weeks could not be predicted by any predictor variables. Conclusions: This research supported previous literature that many HA users do not have adequate HA-SE in important areas (Kelly-Campbell & McMillan, 2015; Kricos, 2000, 2006; Meyer, Hickson, Lovelock, Lampert, & Khan, 2014; Weinstein, 2000; West & Smith, 2007). This research also built on previous work linking HA-SE and satisfaction with HAs (Kelly-Campbell & McMillan, 2015) by showing the ability of MARS-HA scores to predict SADL outcomes. The outcome of future studies could potentially lead to targeted interventions aimed at improving HA-SE, which as a consequence could target increased satisfaction with HAs. If satisfaction with HAs can be improved, it may be possible to see increased uptake and continued use of HAs, which would have the effect of reducing the negative effects of untreated HI.