The Marathon is a high-performing seat with an adjustable fit, making it a solid choice for your child from the #1 brand in safety technology.


  • Safeguards your child with side impact protection, an impact-absorbing base and steel frame
  • Safely installs with easy-on/off lower anchors
  • Easily adjusts with the push of a button – no need to rethread the harness
  • Includes car seat and removable pillow

Rearward Facing

  • Seated shoulder height (9-16.75 inches)
  • Weight (5-40 pounds)
  • Height (0-49 inches)

Forward Facing

  • Seated shoulder height (12-16.75 inches)
  • Weight (20-65 pounds)
  • Height (0-49 inches)

SafeCell Impact Protection - Superior Protection, Only from Britax Britax is the only child car seat brand that features world-class SafeCell Impact Protection. This integrated system of safety components provides unmatched protection for your child. These features include a steel frame, energy-absorbing base, V-shaped tether to minimize seat rotation and staged-release stitches that slow and reduce forward movement during a crash.

Side Impact Protection - Side impacts represent 25 percent of collisions. In fact, it’s these accidents that result in the most severe injuries. We designed the Marathon with these statistics in mind. The seat has a deep foam-lined shell to absorb energy and shield your child from side impacts.

Safe and Easy Installation - At Britax, we make it easy on you to achieve a safe installation. The Marathon’s easy-on/off lower anchors quickly lock onto your vehicle’s anchors and disconnect with the push of a button.

Maximum Fit and Comfort - Britax developed the Marathon to provide a safe and comfortable fit as your child gets bigger. The easy-adjust harness grows along with your child with 10 different positions. Change the height of the seat with just the push of a button – no inconvenient rethreading necessary.