This longitudinal study examines elementary teachers' self-efficacy for science teaching in the years after professional development (PD) ended and during a subsequent 3-year period of follow-up support. Self-efficacy is important because teachers make decisions about classroom activities based, in part, on how confident they are in their abilities to carry out specific instructional strategies. The central research question was, How does teachers' personal science teaching efficacy change during periods with and without PD support? Data sources included semistructured interviews, a self-efficacy assessment, and surveys conducted at five time points. Overall findings show a decline in teachers' personal science teaching efficacy in the years after PD ended. However, during the years of follow-up support, elementary teachers' self-efficacy in science teaching increased and, by the end of 3 years, returned to nearly the same level as when the initial PD ended. Case studies of four teachers highlight the shifts that occurred during the years with and without follow-up support. This study reinforces the need for, and potential value of, providing follow-up support for teachers to sustain PD outcomes over time.