Although colonoscopy is a common examination, there is limited research focusing on how patients experience this procedure. It is important that a colonoscopy is tolerated, as it may lead to lifesaving diagnostics and treatment. This study aims to explore adult patients' experience of undergoing a colonoscopy regarding the time prior to, during, and after the procedure. This was a qualitative study with individual interviews (n = 24) and a purposeful sample that was analyzed using thematic analysis. The analysis revealed four themes. The first, "making up one's mind," describes how the participants gathered information and reflected emotionally about the forthcoming procedure. The hope of clarification motivated them to proceed. In the theme "getting ready," self-care was in focus while the participants struggled to follow the instructions and carry out the burdensome cleansing. The next theme, "going through," illuminates' experiences during the colonoscopy and highlights the importance of feeling involved and respected. The last theme, "finally over," is characterized by experiences of relief, tiredness, and a desire for clarity. The healthcare professionals' ability to meet the participants' needs is vital, given that the experiences are highly individual. These findings contribute to a variegated image of how patients experience the process of undergoing a colonoscopy.