Have you ever reflected on your career or other experiences and thought, if I knew 10 or 20 years ago, what I know now, it would have enabled me to do this or that better-or I would have had a different attitude or perhaps even taken a different path? This article presents the proceedings from the symposium entitled "I Wish I Had Known That! Impactful Guidance and Perspectives for a Fulfilling Career in Toxicology" held at the 2023 annual meeting of the American College of Toxicology. In this session, toxicology professionals reflected on the highlights of their careers, the most impactful advice/mentoring they received or wish they had received, and the characteristics that have been key components of their success. This session consisted of didactic talks from a diverse panel representing various career stages and backgrounds, followed by a panel discussion and the opportunity for the audience to ask questions. Using a structured approach, speakers actively engaged the audience, providing insights gained through their professional journeys. This article offers experiential-based insights to help guide individuals in achieving successful and fulfilling careers in toxicology, considering both professional aspirations and the integration of personal values with life goals.