Crib Mattress Height Adjustment ( Raising and Lowering the Mattress)

Updated December 20, 2025 by Jan of Unique Baby Gear Ideas

Crib mattress height adjustment is one of those small nursery details that becomes very important as your baby grows. Most cribs are designed so the mattress can be raised or lowered over time, allowing parents to start with a higher setting for easy access and gradually move the mattress down as babies become more active. Knowing when and how to adjust the crib mattress height can help prevent awkward lifting, reduce strain on your back, and support a crib setup that continues to work well through different stages.

Go here to see supports and hardware that are available

If you’re here because the mattress feels “too high,” “too low,” or you’re suddenly realizing your baby can sit up or pull up, you’re not alone. The good news is that most height changes are straightforward once you know where the adjustment points are and what to double-check before you tighten everything back down.

Crib Mattress Height Adjustment (Raising and Lowering the Mattress): How It Works

Most standard cribs use a mattress support platform (sometimes called a spring frame) that attaches to the crib with bolts or screws at multiple corners. Those attachment points line up with pre-drilled holes at different heights on the crib frame, which creates the “levels” you see in the manual.

Understanding crib mattress height adjustment helps parents make confident changes without second-guessing whether the mattress is sitting where it should. Once you know how the support platform connects to the crib frame, adjusting the height becomes a practical maintenance task rather than something that feels intimidating or risky.

Some cribs have two levels, some have three, and a few have more. But the idea is always the same: move the support platform evenly so the mattress sits level, then secure it firmly at every attachment point before the crib is used.

Start by finding your crib’s current level and attachment style

Take a close look inside the crib and locate the mattress support frame. You’re looking for the bolts or screws that hold that frame to the crib sides. If your crib uses metal brackets, plastic hangers, or corner hooks, you’ll still see a “fastener point” at each corner where the support is anchored.

If you’ve ever dealt with missing hardware on a crib, you’ll recognize how important those connection points are. If anything looks loose, stripped, or mismatched, pause and address that first before you change levels.

If you need a quick overview of replacement hardware and where to start, visit Crib Parts: Replacement Hardware Help by Brand.

When to Lower a Crib Mattress

Most parents lower the crib mattress in stages, usually right after a developmental “jump” when baby starts sitting, pushing up, or pulling to stand. The exact timing varies by baby, but the pattern is consistent: as mobility increases, the mattress typically needs to go down.

If you want a general reference point for how adjustable crib mattress height is commonly used as babies grow, this overview explains the concept clearly: AAP guidance on choosing a sleep space and using adjustable crib mattress heights.

If your baby is suddenly trying new moves in the crib, it can feel like it happened overnight. One week you’re gently laying them down, and the next week you’re spotting that little knee coming up like they’re practicing for a climb. That’s usually your cue to re-check the mattress height.

Common “it’s time” signs parents notice first

Here are everyday signs that often trigger a mattress height change:

• Baby is sitting up unassisted and rocking or leaning into the rails.
• Baby is pulling up on the rails or trying to stand.
• You notice the top rail feels “too low” relative to baby’s new reach.
• You see extra wiggling during naps, even if nighttime sleep is calm.

How to Lower the Crib Mattress Step-by-Step

This is the simple, practical method most families use. This step-by-step crib mattress height adjustment process is the same one many parents use during routine crib checks, room rearrangements, or after noticing new movement skills. Taking a few extra minutes to adjust the mattress correctly can prevent uneven support and repeated rework later. The key is keeping the mattress support level and re-tightening everything evenly.

1) Clear the crib and remove the mattress

Remove the mattress and anything else in the crib so you can access the support frame easily. This also helps you see the attachment points clearly.

2) Locate all fasteners and loosen them gradually

Most cribs have four corners that must be moved together. Loosen each corner a little at a time rather than fully removing one corner first. That helps prevent the frame from twisting or dropping unevenly.

3) Move the support frame to the next set of holes evenly

Align the frame to the same height setting on all sides. If your crib has three levels, go one level at a time rather than skipping, unless your manual specifically recommends a jump.

4) Reinstall and tighten all hardware in a consistent pattern

Tighten the fasteners in a “cross pattern” the same way you’d tighten lug nuts: corner to corner. This helps the support platform sit square and reduces the chance of a subtle tilt.

5) Re-check for wobble, tilt, or gaps before placing the mattress back in

Before you put the mattress back, press down on the support platform in multiple spots. You’re checking that it doesn’t rock, shift, or flex in a way that suggests a loose corner.

If you want a quick checklist for what to look for on crib hardware and the mattress support area, this is a helpful reference: CPSC crib hardware and inspection tips.

What “Level” Looks Like in Real Life

Go here to see available crib mattress support bolts and replacement hardware

One small detail that saves frustration: take a quick phone photo of each corner before you loosen anything. If your crib uses washers, spacers, or a specific order, that photo becomes your “rebuild map” when you reassemble.

What to Do If You Can’t Lower the Mattress (Or Something Doesn’t Line Up)

If the holes don’t line up, the most common reasons are: the support frame is flipped, one corner is on the wrong level, or the wrong screw/bolt is being used in one corner. Even a small difference in hardware length can throw off alignment.

If you suspect the hardware might be mismatched, these pages can help you narrow it down:

• Are Crib Screws Universal? What Fits and What Does Not
• How to Measure Crib Screws Correctly
• Can You Replace Crib Screws With Hardware Store Screws?

And if your question is specifically about the frame under the mattress (bent rails, missing brackets, or a support that seems unstable), this page ties the pieces together: Crib Mattress Support Frame: What It Is and What Problems Look Like.

Raising the Crib Mattress Again (When It Makes Sense)

In most households, raising the mattress is a short “newborn season” decision. But there are a few times parents revisit it, such as moving the crib temporarily for a new baby, or reassembling after a move and realizing the mattress was left at the lowest setting.

If you’re adjusting the crib for a brand-new setup, it can help to also look at the bigger nursery planning checklist here: Nursery Furniture Planning Guide.

A quick “real-life” reminder before you tighten the final corner

If you’re doing this in the evening, tired, with a baby monitor buzzing in the background, it’s easy to rush the last step. Many parents find it helps to do one final slow check: each corner, each fastener, then a firm press on the support frame before the mattress goes back in.

Typical Mattress Support Frame Attachment Points

See replacement crib hardware kits and tools here

Crib Page Disclaimer

This page is for general information and practical troubleshooting. For your specific crib, always follow the assembly instructions from the manufacturer, use the correct hardware for your exact model, and replace any missing or damaged parts with the proper parts. If you are unsure about fit, alignment, or the condition of any crib component, consider contacting the manufacturer directly or a qualified professional for guidance.

Lowered Mattress Setup for an Active Baby Stage

Go here to see available crib mattress support replacement options

Hi, I’m Jan — the creator of Unique Baby Gear Ideas. I love helping expecting parents discover nursery décor inspiration and creative photo shoot ideas that make every stage of pregnancy feel beautiful.

Over the years, I’ve helped thousands of parents choose safe, stylish nursery furniture through hands-on reviews and real-world testing.

The suggestions I share here come from years of hands-on experience styling nurseries, reviewing maternity gowns, and learning what makes each photo session shine.

All articles and images on Unique Baby Gear Ideas are personally reviewed and edited by Jan Bay. Modern creative tools may assist with design or drafting, but every final page reflects my own voice, experience, and editorial judgment.