Killings by juvenile homicide offenders (JHOs) who use accomplices have been increasing since the 1980s and currently represent approximately half of juvenile arrests for murder in the United States. Nevertheless, prior research has not compared JHOs who kill alone with JHOs who kill in groups. The present research followed up 30 years later on a sample of 59 male murderers and attempted murderers sentenced to adult prison. This study was designed to analyze whether lone and group JHOs differed on pre‐incarceration, incarceration, and post‐incarceration variables. Significant findings indicated that compared with lone offenders, group JHOs had a higher mean of pre‐homicide arrests and were more likely to be Black, have a pre‐homicide delinquent record, commit a crime‐related homicide offense, and target a stranger. With respect to post‐homicide variables, group JHOs were more likely to be released from prison and more likely to be rearrested. The two types of JHOs did not differ significantly in relation to the number of post‐release violent offenses. Preliminary implications of the findings and avenues for future investigation are discussed. Copyright © 2016 John Wiley & Sons, Ltd.