At the beginning of the competition season, FIRST LEGO League sends official materials to each registered team, consisting of a 'challenge mat', LEGO bricks, and instructions for building the items for the mat (collectively known as the Challenge Set, formerly the Field Setup Kit). The teams also receive a list of tasks, called 'missions', to complete involving each model on the mat (i.e. taking a loose piece from one model and placing it inside another). FIRST LEGO League gives teams complete freedom on how to complete the missions, providing that they are completed by a programmed LEGO Mindstorms robot with no outside assistance. The robot has two and a half minutes to complete the missions; called the Robot Game. Each team has a minimum build period of 8 weeks to analyze the challenge mat, design and build a LEGO Mindstorms robot, and program it to fulfill the given missions in any manner they see fit. The robot must be autonomous,[4] and may contain only one LEGO Mindstorms programmable block and no more than 4 motors.

In addition to the live robot run, or Robot Game, the competition has three additional judged sections with the purpose of providing teams with feedback on their achievement of the FIRST LEGO League learning objectives. The first judging session, Core Values,[2] is designed to determine how the team works together and uses the FIRST LEGO League Core Values in everything they do, which include inspiration, teamwork, Gracious Professionalism, and Coopertition. In addition to discussing how their team exhibits these values, teams are also asked to perform a teamwork activity, usually timed, to see how the team works together to solve anew problem. Secondly, in the Robot Design, or technical judging,[2] the team demonstrates the mechanical design, programming, and strategy/innovation of their robot. The goal of this judging session is to see what the robot “should” do during the Robot Game. Thirdly, in the Project,[2] the students must give a 5-minute presentation on research a topic related to the current challenge. The required steps of the project as teams to first identify a problem that is related to the topic of that year's competition, then create an innovative solution to their identified problem by modifying something that already exists or creating something completely new (an "innovative solution"), and then they must share that solution with others, such as real world professionals who have expertise in the annual challenge theme.[5]

When the official competition convenes, each team brings their robot to compete on an official challenge mat identical to their own. Two members of the team are allowed at the board during a match; however, they can switch out if needed. In the case of a serious problem, such as the entire robot breaking down, the entire team is allowed at the board for as long as the problem persists. Members are not permitted to bring additional robots or board items from other practice tables to the board during competition.

The robot starts in an area marked as 'base', a white area in the corner or to one side of the table. In base, two team members are allowed to touch the robot and start program. If the team touches the robot while it is outside of base (an 'interruption'), the referee will issue a penalty, resulting in a 5-point deduction. These are stationary LEGO models that negate the final score if they remain until the end, providing an incentive to not interrupt the robot. The robot is not required to return to base; some teams have completed all their missions without returning to base during the time allowed to complete the missions. 

FIRST LEGO League teams use LEGO Mindstormskits to construct their robots. The robots are programmed using one of the block-based programming environments: the official EV3 software, the official NXT-G software (now outdated), or Robolab. All these are built around Labview.