Most child sexual abuse (CSA) remains unreported and undetected. Despite this, much of what we know about perpetrators of CSA is derived from samples of convicted CSA offenders. Significant knowledge gaps remain about those who have evaded detection. This study addresses this gap with an in-depth content analysis of the case files of ten convicted child sexual offenders (CSOs) with the longest detection lag, selected from a broader group (n = 349) of men incarcerated at the Massachusetts Treatment Center (MTC). Participants were examined on a range of offender characteristics including Adverse Childhood Experiences (ACEs), cognitive distortions, antisocial traits, indicators of pedophilia and Machiavellian or narcissistic traits, offense facilitating factors, and grooming behavior. A tentative profile emerged with the following characteristics: direct experience of childhood abuse, various cognitive distortions, specialized rather than versatile criminal history, pedophilic traits, Machiavellian traits, and engaging in a range of offense-facilitating behaviors including grooming. We provide insight into offenders who evade detection for CSA and set the foundation for further research to inform prevention strategies for law enforcement agencies and child-serving organizations.