2012 World Junior Championships in Athletics – Men's 4 × 400 metres relay

The men's 4 × 400 metres relay at the 2012 World Junior Championships in Athletics was held at the Estadi Olímpic Lluís Companys on 14 and 15 July.

Records
, the existing world junior and championship records were as follows.

Heats
Qualification: First 2 of each heat (Q) plus the 2 fastest times (q) qualified

Participation
According to an unofficial count, 76 athletes from 18 countries participated in the event. • 🇦🇺 australia (4)

• undefined (4)

• 🇨🇦 canada (4)

• 🇫🇮 finland (4)

• 🇩🇪 germany (4)

• 🇬🇭 ghana (4)

• 🇮🇳 india (4)

• 🇮🇹 italy (5)

• 🇯🇲 jamaica (5)

• 🇯🇵 japan (4)

• 🇳🇴 norway (4)

• 🇵🇱 poland (5)

• 🇷🇺 russia (4)

• undefined (4)

• undefined (4)

• 🇪🇸 spain (4)

• undefined (4)

• 🇺🇸 united states (5)