Purpose Earlier studies tried to predict and explain adult-onset offending, most often by comparing risk factors for juvenile and adult onset of criminal behavior. Little is known, however, about how criminal careers of adult-onset offenders develop. The aim of this study is to describe and compare juvenile-and adult-onset criminal careers of both men and women in terms of frequency, intensity, duration, recidivism, crime mix, seriousness, and specialization. Methods Using a sample of 43,338 offenders who all had a criminal record in 2013, criminal careers are reconstructed retrospectively up to age 12 and prospectively up to the 1st of July, 2014. Male and female juvenile-and adult-onset offenders are identified and compared on the abovementioned parameters of their criminal careers. Results Compared to all other groups, female adult-onset offenders commit fewer crimes, offend at a lower rate, desist from crime earlier, have lower recidivism risks at least up to the tenth crime, commit different types of offenses, commit more minor and less serious crimes, and are more specialized in the types of crime they commit. Male juvenile-onset offenders have the most serious career in terms of these career dimensions. Conclusions Criminal careers of adult-onset offenders, both men and women, develop differently on all dimensions. Implications for life-course criminological theories and prevention strategies are discussed.Keywords Adult-onset offending . Criminal career dimensions J Dev Life Course Criminology (2018) 4:92-119 https://doi