Crohn's Disease (CD) is a gastrointestinal disease that can cause chronic diarrhea with or without gross bleeding, abdominal pain, weight loss, and fever. This study will assess the pharmacokinetics, efficacy, and safety of risankizumab in pediatric participants with moderately to severely active CD aged 2 to \< 18 years old who have had intolerance or inadequate response to other therapies. Risankizumab is an approved drug for adults with plaque psoriasis, psoriatic arthritis, and CD and is being developed for the treatment of CD in pediatrics. This study is comprised of 3 cohorts that may participate in 3 substudies (SS). Cohort 1 will enroll participants with ages from 6 to less than 18 years. Cohort 2 will enroll participants with ages from 2 to less than 6 years. Cohort 3 will enroll participants with ages from 2 to less than 18 years. SS1 is an open-label induction period where participants will receive a weight-based induction regimen of risankizumab. SS2 is a double-blind maintenance period where participants will be randomized to receive 1 of 2 doses of weight-based induction regimen of risankizumab. SS3 is an open-label extension period where participants will receive risankizumab based off of their response in SS2. Around 110 pediatric participants with CD will be enrolled at around 100 sites worldwide. Participants in SS1 will receive risankizumab intravenously during the 12-week induction period. Participants in SS2 will receive risankizumab subcutaneously during the 52-week randomized maintenance period. Participants in SS3 will receive risankizumab subcutaneously during the 208-week open label period. Participants will be followed-up for approximately 140 days. There may be higher treatment burden for participants in this trial compared to their standard of care. Participants will attend regular visits during the study at a hospital or clinic. The effect of the treatment will be checked by medical assessments, blood tests, checking for side effects and completing questionnaires.