Introduction: Knowledge of how perceptions of personal control change over time may provide valuable insights into how people cope with having dementia. The present study aimed to examine change in locus of control over a 12-month period in persons with dementia. Method: The study included 52 participants with dementia. Locus of control was measured with the Locus of Control of Behavior Scale (LoCB), with higher scores indicating a more external locus of control, interpreted as perceiving less personal control. A ≥5% change on the LoCB was considered clinically meaningful. We recorded sociodemographic characteristics and assessed dementia severity, cognition, ability to function independently in daily activities and physical self-maintenance, depressive symptomatology, and number of prescribed medications. Analyses were performed to examine differences between those with increases (more external) or decreases (less external) in the LoCB score after 12 months and to examine associations between baseline variables and change in the LoCB score. Results: The mean LoCB score for the total sample did not change after 12 months (baseline mean 29.33 vs. follow-up mean 30.33, p = 0.553); however, 2 subgroups emerged. Using the ≥5% cutoff revealed that the LoCB score changed for 92.3% of the sample, becoming less external (lower LoCB) for 21 participants and more external (higher LoCB) for 27 participants. At baseline, the mean LoBC score was higher in the group that became less external (33.81 vs. 24.56), p = 0.006, while this was reverse at follow-up (23.57 vs. 34.41), p = 0.001. Dementia severity and dependence in physical self-maintenance increased during the 12 months in both groups. Among those becoming more external, we also found a decline in cognition (p = 0.002), an increase in dependence in daily activities (p = 0.003), an increase in the use of prescribed medication, and a decrease in depressive symptomatology (p = 0.003). The baseline LoCB score was the only variable associated with 12-month change in LoCB scores (p = 0.001). Conclusion: Most participants showed a clinically meaningful change in locus of control after 12 months. Those with more signs of dementia progression reported a decrease in personal control but also a decrease in depressive symptoms. These findings are interesting for our understanding of coping but must be replicated with a larger sample.