2nd Seat Kit 3.0

Why We Love It

The 2nd Seat Kit converts your Single-to-Double Stroller into double mode to make room for two kiddos, from newborns to toddlers. It installs in just a few clicks with no tools needed, and it’s easy to change up your seating arrangements as your kids’ preferences change — sometimes multiples times per day  

And unlike some double strollers with a lower weight limit in the second seat, our 2nd Seat Kit supports 45 pounds in both seats, so you can stroll in double mode for much longer.

Setups for every age and stage

The 2nd Seat Kit offers flexible configurations that work for every stage, without the limitations or compromises common in many convertible strollers. Every setup is designed to be comfortable and practical for both kids and parents.

Infant + Toddler

Many double strollers with Bassinet attachments require you to put the Bassinet in the lower position, so your baby is riding just a few inches above the ground.

Our Bassinet goes in the top position, so you can easily see and care for your infant, while your older child goes up front, and can face forward or toward you.

You can also use the Car Seat Adapter, or the stroller seat with Infant Seat Insert in the upper or lower position.

Two Toddlers

Most strollers' add-on seats have a lower weight limit than the included seat, so parents typically have to put their smaller child in the lower position.

Our 2nd Seat is identical to the seat included with the Stroller, with a weight limit of 45 lbs for each seat when used in double mode. Both seats can face either direction, giving you four different two-seat configurations.

Twins

The Single-to-Double Stroller is a favorite among twin parents. To stroll with twin infants, you can use the 2nd Seat Kit + two Car Seat Adapters or two Infant Seat Inserts.

As your twins get older, you can face both kiddos forward, both toward you, facing each other when they're getting along, or facing away from each other when they're not!

New for 2026: The 2nd Seat Kit 3.0

The 2nd Seat Kit 3.0 is packed with the same seat upgrades as the Single-to-Double Stroller 3.0, making every stroll even more comfortable for your child and convenient for you.

▶️ Click the play button on any feature to see it in action!

Built-in LegShade™

An all-new LegShade™ (only found on Mockingbird strollers) pulls out from the beneath the seat and provides sun protection for little legs. It's particularly useful for babies who are too young to wear sunscreen.

Magnetic harness

The new magnetic buckle clicks together like magic, making it easier to secure a wiggly toddler and get moving.

Reversible seasonal seat liner

The dual-sided seat liner flips from a cushioned everyday side to a breathable mesh side for cool comfort (and is machine-washable for easy cleaning).

Height-adjustable canopy

The canopy extends upward for a few extra inches of headroom, which can an additional year of strolling.

Additional in-seat pockets

Two new in-seat pockets are perfect for snacks, toys, or tiny treasures. We've also increased the size of the seat-back phone pocket and added a stash pocket for essentials.

Thoughtful upgrades

Reflective piping for nighttime visibility, softer strap fabrication, and new frame and canopy colors make the 3.0 our most refined stroller system yet.

Features & Use

The 2nd Seat Kit 3.0 comes with one seat, a set of upper adapters (to raise your 1st Seat and make room for the 2nd), and a set of lower adapters (to attach the 2nd Seat).

The adapters can be installed in under a minute and removed just as quickly, so you can easily switch from single to double mode and back again.

The 2nd Seat Kit 3.0 comes with all of the updated features of our 3.0 strollers, including Mockingbird's FullShade™ System, reversible seasonal seat liner, and an updated harness with magnetic buckle, softer straps, and reflective piping for safer nighttime strolling.

Compatibility

The 2nd Seat Kit 3.0 is compatible with all models of the Mockingbird Single-to-Double Stroller, but cannot be used with the Mockingbird Single Stroller. If you're unsure about which model you have, feel free to contact our product specialists.

Strolling with an infant + toddler:
To stroll with an infant and an older kiddo, you’ll need the 2nd Seat Kit to make room for two riders, as well as one of our three infant accessories (strongly recommended until your newborn develops head and neck support). You can choose from Mockingbird’s cozy lie-flat Bassinet, the practical space-saving Infant Seat Insert, or one of our convenient Car Seat Adapter, which is compatible with over 35 popular infant car seats (all sold separately).

Strolling with two infants:
For twins, we recommended using the 2nd Seat Kit 3.0 with two Infant Seat Inserts or with two Car Seat Adapters.

Age, Weight, & Height Guidelines

Unlike other two-seat strollers, our top and bottom seats are identical, so they have the same weight limit. You can use both seats with children up to 45 lb. The maximum headroom from the seat to the canopy is about 20".

Care & Cleaning

To clean, wipe with a damp cloth and mild detergent (if necessary).

The reversible seat liner is machine washable, and other stains can be removed by wiping clean.