Onesies vs Rompers Explained for New Parents

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The terminology around infant clothing can be confusing.

If you don’t know the difference between a onesie and a romper, you’re not alone!

To further confuse matters, these types of baby clothes may also be referred to as body suits, creepers, jumpsuits, vest, playsuits, or pajamas. And the words used may be different depending on where you live.

Knowing the difference between a onesie vs romper is useful, even if it’s just so you can tell family members who want to help out what you might need (or when you go to load up your baby registry).

The main difference between a onesie and a romper is the legs. A onesie doesn’t have any legs, just two or three snap fasteners at the crotch, whereas a romper can have short or long legs and sometimes feet.

A onesie is generally worn underneath pants, a skirt or dress, or even a swaddle sack — but a romper is a full outfit by itself.

Let’s take a closer look at when you might need each one!

When to wear a onesie or a romper

When to dress your baby in a romper versus a onesie will depend on several factors such as the climate and the time of day.

In hotter climates (especially those that don’t have great air-conditioning), it makes sense for a baby to wear just a onesie at night to keep them cool.

In the daytime when it’s warm, a short-sleeved and short-legged romper will keep your baby cool while also providing enough skin coverage for trips out in public.

In colder weather, a short- or long-sleeved onesie is a good base layer to use under a warm outfit such as pants, a t-shirt and a sweater.

Babies will usually need to wear a onesie underneath their swaddle sack to keep them warm at night unless the weather is exceptionally warm.

Onesies are great for:

  • Being around the house (especially when warm)
  • Layering in the cold
  • Wearing at night under a swaddle
  • Substitute for a t-shirt, to be worn with pants or a skirt

Rompers are ideal for:

  • Quick, one-piece outfit that’s easy to put on
  • Easy-access for diaper changes
  • Simple but stylish outfit for warm weather

What is a onesie?

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A onesie is a one-piece garment that is usually worn by a baby or toddler.

It has snap fasteners at the crotch and may or may not have sleeves, but does not have any legs.

A onesie may be worn as a vest underneath an outfit in cold weather or in place of a t-shirt with a pair of shorts when the weather is warm.

Other names for a onesie:

  • Body suit
  • Creeper
  • Vest

Onesies are popular for baby boys and girls and come in various styles, from plain baby vest with no sleeves to fancy patterned shirts.

Some onesies are obviously meant to be worn as underwear, some can only be worn as outerwear and there are some which could work as either.

For babies, a onesie is much more practical than a t-shirt because it will stay tucked in without riding up, which is more comfortable for the baby.

Onesies come in every size from preemie baby and newborn up to about age three.

The reason why onesies aren’t available in larger sizes than age three is because by that age most kids are potty training and that wouldn’t be practical to do in a onesie!

TIP: If you ever need to change a toddlers’ diaper when they are wearing a onesie and won’t lie down, let them stand up but fasten the poppers over one shoulder.

This keeps the onesie out of the way so you can change the diaper without the onesie dangling in the way.

Pros and cons of onesies


  • Comfort: Onesies are very comfortable for babies as they stay in place when they move around
  • Good for cold weather: A long-sleeved onesie provides an excellent base layer for the winter
  • Good for hot weather: A short-sleeved onesie is the coolest nightwear when its very hot


  • Not always visible: Many onesies come with cute prints and slogans which are wasted if they are worn only as underwear
  • Revealing: A onesie isn’t great to be worn on its own as the baby’s legs will be out

What is a romper?

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A romper is a one-piece garment which is worn by babies and young children.

Rompers have sleeves and legs, which may be short or long.

They are closed using zips, buttons or snap fasteners. A romper may be worn as a pajama or as a complete outfit.

Other names for a romper:

  • Romper suit
  • Jumpsuit
  • Playsuit
  • Baby pajama

Rompers are incredibly comfortable, which is why they are most popular with parents of newborns.

After the first few weeks or months, parents may begin to dress their babies in smarter clothes in the daytime and use rompers only at night time for sleeping.

That said, there are some incredibly cute romper suits which can definitely be worn as daywear.

Short sleeved and short-legged rompers are perfect to wear in warm weather because they cover enough skin to function as an outfit, while being light enough to keep cool.

Rompers have fasteners along the inside of the legs and around the crotch. This makes it easy to change a diaper without taking it off. Some rompers also have fasteners all the way up the front, but not all do.

Baby rompers come in a variety of sizes from preemie baby and newborn up to toddler. Older kids and even adult women may also wear rompers in place of pants and a top.

TIP: For toddlers, avoid rompers with built-in feet as these can be very slippy on hard floors. Some rompers have grips on the feet, but nothing grips as well as bare feet!

Pros and cons of rompers


  • Good for hot weather: A short-sleeved romper is a complete one-piece outfit that will keep your baby cool
  • No need for socks: Rompers with built-in feet are great for night-time because baby socks are hard to keep on
  • The cute factor: Is there anything cuter than a baby in a romper?


  • Can look like nightwear: As rompers are often worn as pajamas, it could look like you didn’t bother to get your baby dressed for the day!
  • Awkward to put on and take off: Rompers have a lot of snaps (or poppers). And if you line the first one up wrong you have to start over, which is frustrating
  • Difficult to use when potty training: One kids start potty training they usually stop wearing rompers as it’s tricky to unfasten them

Wrapping Up

Don’t be confused by sleeves or no sleeves, daywear or nightwear, underwear or outerwear.

The main difference between rompers and onesies is that rompers have legs and onesies don’t.

Unless you live in the UK, of course, in which case onesies have legs and the ones without legs are called vests!

You’ll likely want to load up with plenty of both onesies and rompers for your baby. Onesies are versatile and are great for layering, wearing underneath swaddles while sleeping, or being around the house when it’s hot.

Rompers are an easy, one-piece outfit you can throw on baby any time!

Before you go, check out more explainers like:

Hope this helps!