Thinking in words, inner voice, is a common phenomenon with many positive uses. However, it is also a feature of different symptoms of psychopathology, such as rumination and worry. Knowledge on inner voice could aid the development of therapeutic tools, yet research has largely ignored the basics of inner voice, such as prevalence and association with psychopathological symptoms in the general population. The present study used a Finnish population-based sample consisting of 9,753 individuals to examine the association between how frequently one experiences one’s inner voice and symptoms of depression, anxiety, and psychosis. The results showed that inner voice is a common phenomenon: only 1.9% of the women and 4.0% of the men reported that they never use inner voice. Both correlation and multilevel regression models showed a significant and positive association between survey scores on a question on inner voice activity, and scores on subscales from both The Brief Symptom Inventory 18 (depression and anxiety) and the Symptom Checklist-90-Revised (psychosis) in both men and women. In other words, using one’s inner voice more frequently was associated with increased symptoms of psychopathology. The results of the present study support the idea that there is reason to further examine the possibility to train inner voice as a therapeutic tool.