There are five different age groups, known as "sections", within the organisation for the UK:

• Anchors - 5 to 8 years (companies need special permission to accept boys younger than 5 years old)
• Juniors - 8 to 11 years
• Company - 11 to 15 years
• Seniors - 15 to 18 years
• Amicus - 15 to 22 years

(Companies may choose to run a Girls' Association alongside or in combination with these sections)
Within Australia there are three sections known as:

• Anchors - 4 to 7 years
• Juniors - 8 to 11 years
• Seniors - 12 to 18 years

Seniors is divided into 2 groups based on age. 12-14 Alpha and 15 - 18 Omega
Age groups are typically based on school years, so boys in the same year group would be promoted to the next section together, regardless of the dates of individual boys' birthdays. In some companies, sections may merge or there may be minor variations to the normal age boundaries, to accommodate excessively large or small groups of boys or a lack of leaders. Boys might also move to their next section before the end of the year to allow a smoother transition.
Amicus was launched in 1994, and is intended to either run as an alternative to the Seniors programme or even without any other Boys' or Girls' Brigade sections operating. Unlike other sections which may be for boys only in many companies, Amicus is always run as a mixed-gender group. The Amicus concept emphasises involvement of all its members in decision-making concerning the running of the section, such as the content and whether a uniform is to be worn. The section will be overseen and supervised by leaders aged over 18, who receive training from the Boys' Brigade and may deliver parts of the programme.^[16]
Malaysia has three age group which are

• Pre-Juniors - 5 to 7 years
• Juniors - 8 to 11 years
• Seniors - 12 to 18 years

In the United Kingdom and Eire The BB is divided into 4 Regions, each region is then further divided. In Scotland and England & Wales The BB is divided into Districts and then Battalions. In Northern Ireland the BB is divided into 13 Battalions. The Battalions provide a local grouping of companies. The Battalions are normally based on Cities or Counties. Each Battalion has its own local structure that organises events and training on behalf of the member companies.

Leadership

Officers (adult leaders)

Leaders in training are Warrant Officers, attaining the rank of Lieutenant only when having completed additional formal training in youth leadership. To avoid unnecessary leader hierarchy, all qualified officers are Lieutenants. The post of Captain of a company is a brevet rank with those in the position reverting to Lieutenant when they cease to be in the position; similarly other positions such as the company Adjutant (second to the captain) are considered appointments rather than substantive ranks.
Boys bearing the rank of Staff-Sergeant are non-commissioned officers but act within the company as Officers.

Boys as Non-Commissioned Officers

An older boy can gain promotion from Private to become a Non-Commissioned Officer (NCO). There are four NCO ranks available, each being awarded when a boy is of a certain minimum age and reaches a high enough standard of leadership:

• Lance Corporal (minimum age 14)
• Corporal (minimum age 15)
• Sergeant (minimum age 16)
• Staff Sergeant (minimum age 17)

NCOs often play an important role in the Boys' Brigade, helping the officers and other adult helpers with organising activities and awards classes, particular in the Anchors and Juniors sections. NCOs wear chevrons on their upper right arm.
Staff Sergeants act within the company as officers and do not stand in the ranks; however as Staff Sergeants are boys of the Brigade, they can still partake in company activities and competitions, and still earn awards and badges. The uniform of Staff Sergeants is slightly different from that of the normal boy or NCO, they wear still wear a blue shirt. If caps are worn, the BB Anchor is used with no coloured surround. Their rank is denoted with an armband on the right forearm with four inverted chevrons (similar to the rank badge historically worn by senior grades of sergeant in the British Army).
In the United Kingdom, those aged 17 to 21 years old who are nominated by their company, may participate in The Boys' Brigade KGVI Youth Leadership Training;^[17] this consists of two one-week-long residential training experiences containing all the training needed to become an officer in The Boys' Brigade. KGVI is held at each of the Regional Headquarters (Felden Lodge in England/Wales, Carronvale House in Scotland and Rathmore House in Northern Ireland).