How to assemble a crib safely. A step-by-step guide every new parent can trust.

There you are, standing in the nursery with three bags of hardware and a manual that opens to a parts diagram printed in a font made for younger eyes. Getting the crib safely assembled is one of those tasks where the details genuinely matter, and you deserve to walk away from it completely sure.

This is how to do it right, from the box to the first sleep.

Here is what is actually going on

A crib is the one piece of nursery furniture where correct assembly is directly tied to safe sleep. The guidelines that pediatricians follow for newborn sleep (firm surface, no gaps, no loose items) all build on the assumption that the crib itself is solid and correctly put together. That is the foundation everything else rests on.

The good news: crib assembly is very learnable. Manufacturers test these designs extensively, and the steps are written to be followed without professional help. What trips people up is not complexity. It is skipping the manual, working with a second-hand crib that has missing hardware, or adding pieces that were never designed to be there. All of those are preventable.

For more on creating a complete safe sleep environment, the safe crib setup guide for newborns covers what goes in alongside the assembled frame.

When to set up the crib and how the crib mattress height changes

Most parents set the crib up a few weeks before the baby arrives, which gives time to sort out any missing parts without a deadline. Start with the mattress support at the highest position. That is where it stays for the first few months, while she cannot yet pull herself up or stand.

You will lower it in two stages as she grows. Move it down one level when she starts pulling to stand, usually somewhere around 8 to 10 months. Then bring it to the lowest position once she can stand independently. Each adjustment is as important as the original build, so keep the hardware packet somewhere you can find it.

This is a three-stage process across the first couple of years, not a one-and-done task.

How to tell your crib assembly is done right

Run through this list when you think you are finished:

• The crib does not wobble or shift when you press firmly on all four corners
• Every bolt, screw, and fastener is actually tight (not hand-tight, properly tight)
• The mattress fits snugly, with no more than two fingers of space between its edge and any side of the crib
• The mattress surface is firm and springs back when you press it flat
• There are no protruding edges, splinters, or hardware that sticks out
• If the crib has an adjustable side, it locks solidly in position

If anything does not pass, fix it before the first sleep. One loose bolt matters.

Things that actually help

Read the full manual before picking up a single piece

Not the summary page. The whole thing. Manufacturers put critical steps mid-way through, and knowing the full sequence before you start means you catch the moments where two people are genuinely needed and the moments where the order of assembly is not negotiable.

Lay out every piece and count the hardware first

Before anything goes together, spread every component on the floor and check it against the parts list. If something is missing, call the manufacturer. Most companies ship replacement hardware free of charge and will expedite it. Better to find out before the mattress is waiting.

Use the correct tools

Crib hardware is almost always metric. An ill-fitting wrench can strip a bolt head and leave a fastener that looks tight but is not. Use the Allen keys or spanners that came with the crib, or check the exact sizes before substituting from your own toolkit.

Do the wobble test before placing the mattress

With the frame together and before the mattress goes in, press firmly on each corner. Nothing should shift. Then check every joint by hand. Wobble is much easier to fix at this stage than after the mattress and bedding are in place.

Keep the hardware packet somewhere memorable

You will need it again at each mattress height adjustment. Tape it to the inside of a drawer, attach it to the manual, or put it in a labeled bag. The outer packaging goes, but the hardware stays.

Tonight could be the night it clicks

Willo has 12 sleep sounds built for little ones, a bedtime routine that tracks itself, and a sleep plan matched to your baby's current phase. When nothing's working at 2am, you'll be glad it's on your phone.

Get Willo App

Things that tend not to help

Assembling without the original manual. If you have a second-hand crib and the manual is unavailable, check the manufacturer's website. Many post PDFs for older models. If you cannot find it and the crib predates 2011, it is worth checking the CPSC recall database before going further, since crib safety standards changed substantially that year.

Adding padding, bumpers, or inserts. They are not part of the assembly, and they are not safe inside the crib. For a newborn, the crib holds a firm mattress, a fitted sheet, and nothing else. The safe sleep practices guide covers why in plain language.

Tightening bolts by feel. Bolts that feel snug by hand can still be under-torqued. Use the tool that came with the crib and turn until there is genuine resistance. If the manual specifies a torque value, follow it.

Skipping the recall check for any second-hand crib. The CPSC database is searchable by brand and model at cpsc.gov. Two minutes of checking is worth it.

When to stop reading articles and call your pediatrician

Crib assembly itself is generally outside the pediatrician's scope, but do contact your crib manufacturer or the CPSC if:

• Parts are missing and the manufacturer cannot supply them
• You find the model in the CPSC recall database
• The crib shows structural damage or joints that will not tighten properly
• You are working with a crib from before 2011 and are not certain about its safety status

Your pediatrician is also the right person to ask if you are unsure whether a specific sleep setup is safe for your baby. They will not mind being asked.

How Willo App makes this easier

Once the crib is ready and your baby is home, Willo App walks alongside you through all 35 phases of those first years of sleep. You will see when to lower the mattress support, what her current developmental phase means for sleep, and which sounds genuinely help her settle. For anyone weighing whether to start in a bassinet first, the bassinet vs crib guide covers the tradeoffs clearly.

Ask Willo is there for the questions that come at 2am, long after the assembly instructions are folded away.

The crib is ready. She is almost here.