The Adolescent Brain Cognitive Development (ABCD) study is recruiting and following over 10,000 9-10 year olds through adolescence to track brain development and health. The imaging component of the study, developed by the ABCD Data Analysis and Informatics Center (DAIC) and the ABCD Imaging Acquisition Workgroup, includes imaging methods and assessments optimized and harmonized across 21 sites to measure brain structure and function relevant to adolescent development and addiction. This article provides an overview of the imaging procedures, their selection, and preliminary quality assurance and results, demonstrating the feasibility and age-appropriateness of the procedures and generalizability of findings to existing literature. The study aims to identify developmental trajectories and neural signatures for adolescent mental health, with a focus on early signs of externalizing and internalizing symptoms. The imaging protocol includes 3D T1- and 3D T2-weighted images, diffusion-weighted images, and resting-state and task-based functional MRI. Task-based fMRI assessments include the Monetary Incentive Delay (MID) task, the Stop Signal task, and an emotional version of the n-back task, measuring reward processing, motivation, impulsivity, impulse control, working memory, and emotion regulation. Preliminary data show promising results, with high completion rates and reliable brain activity patterns. The ABCD study follows an open science model, releasing data monthly and annually to the research community.The Adolescent Brain Cognitive Development (ABCD) study is recruiting and following over 10,000 9-10 year olds through adolescence to track brain development and health. The imaging component of the study, developed by the ABCD Data Analysis and Informatics Center (DAIC) and the ABCD Imaging Acquisition Workgroup, includes imaging methods and assessments optimized and harmonized across 21 sites to measure brain structure and function relevant to adolescent development and addiction. This article provides an overview of the imaging procedures, their selection, and preliminary quality assurance and results, demonstrating the feasibility and age-appropriateness of the procedures and generalizability of findings to existing literature. The study aims to identify developmental trajectories and neural signatures for adolescent mental health, with a focus on early signs of externalizing and internalizing symptoms. The imaging protocol includes 3D T1- and 3D T2-weighted images, diffusion-weighted images, and resting-state and task-based functional MRI. Task-based fMRI assessments include the Monetary Incentive Delay (MID) task, the Stop Signal task, and an emotional version of the n-back task, measuring reward processing, motivation, impulsivity, impulse control, working memory, and emotion regulation. Preliminary data show promising results, with high completion rates and reliable brain activity patterns. The ABCD study follows an open science model, releasing data monthly and annually to the research community.