Last updated: August 21, 2026
There is a line that turns up in serger reviews often enough to be a genre of its own: everyone seems to think a serger is a mysterious machine, and it is not. The mystery is almost entirely the threading, and the threading is a sequence of four paths done in a fixed order. Do them in order and the machine chains off perfectly. Do them out of order and you get a tangle you will blame on the machine.
This is the sequence, the reason the order matters, and the tie on method that means you almost never have to do the full thread again. Nothing here needs a tool you do not already have, other than a pair of tweezers.
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Quick Answer
How do you thread a serger?
- In this order, every time: lower looper, upper looper, right needle, left needle.
- Presser foot up before you start, so the tension discs are open and the thread can seat between them.
- Follow the color coded path on the inside of the door, and pull each thread until you feel it click into every guide.
- To change color later, tie the new thread to the old tail and pull it through instead of rethreading.
Bottom line: the order is not a preference, it is mechanical. Threading the upper looper before the lower one traps the lower thread and nothing will chain.
Why the Order Is Not Optional
The two loopers cross each other under the needle plate. The lower looper swings up and behind the upper looper, so if the upper looper is threaded first, its thread lies across the path the lower looper has to travel. The lower looper thread then sits on the wrong side of the crossing and the stitch cannot form.
That is the whole reason for the sequence, and it explains the most common beginner failure: the machine sews, the knife cuts, and the chain simply falls apart behind the foot. Nothing is broken. The two looper threads are on the wrong sides of each other.
Set Up Before You Thread
Raise the presser foot so the tension discs open. Turn the handwheel toward you until the needles are at their highest point. Open the front door and the side cover so you can see the looper eyes, and set your tension dials to the standard number marked on the machine before you begin.
Step One: The Lower Looper
Start here, always. Run the thread from the cone up through the telescoping thread stand, through the guide bar and into the color coded path for the lower looper. Follow the path through the tension disc, down behind the front panel, along the guides and out to the looper eye at the far left.
The eye is the hard part, because it sits behind the knife in a gap your fingers will not fit into. This is what tweezers are for. Push the thread through from the front, pull about six inches out the back and lay it toward the left, out of the path of the upper looper.
If the Looper Will Not Sit Still
Turn the handwheel toward you a little until the lower looper swings out to the right, where the eye is easiest to reach. Many machines also have a small lever that swings the lower looper forward for threading. Check the manual for your model, since the mechanism varies between machines.
Step Two: The Upper Looper
Same route, one path over. Take the thread up the stand, through the guide bar, into the second color coded channel, down through its tension disc and along the guides to the upper looper eye, which sits higher and is usually the easier of the two to reach.
Pull six inches through and lay this tail toward the left as well, on top of the lower looper thread. With both loopers threaded in the correct order, turn the handwheel by hand one full turn and watch the two threads pass each other cleanly. If they snag, one of them jumped a guide.
Step Three and Four: The Needles
Right needle first, then left. Both follow the same style of path: up the stand, through the guide bar, into their tension disc, down the front and through the guides above the needle bar. Thread each needle from front to back and leave the tails hanging to the back under the foot.
If you are sewing a three thread overlock you use one needle only, and the manual tells you which one for the stitch width you want. Remove the unused needle rather than leaving it in and unthreaded, so nothing catches.
The Test Chain
Lower the presser foot, hold the four tails loosely toward the back, and turn the handwheel slowly for a few stitches. A chain should start forming behind the foot. Once it does, run a slow test chain of a few inches with no fabric, then sew a scrap. If the chain forms in the air but falls apart on fabric, the problem is tension, not threading.
Threading Order and What Goes Wrong
The failures are as predictable as the sequence. Each of the four paths has one classic mistake attached to it, and recognizing the symptom saves you from starting the whole thread over.
| Step | Path | Classic mistake | What you see |
|---|---|---|---|
| 1 | Lower looper | Threaded after the upper looper | Chain falls apart behind the foot |
| 2 | Upper looper | Thread skipped a guide near the eye | Loose loops on the top of the edge |
| 3 | Right needle | Not seated in the tension disc | Loops on the underside of the seam |
| 4 | Left needle | Threaded back to front | Skipped stitches, thread shreds |
Threading paths and looper mechanisms differ between models, so the guide positions above are the general layout of a home serger and your manual is the authority for your machine.
The Tie On Method for Color Changes
Once the machine is threaded correctly you rarely repeat the full sequence. Cut the old thread just above the cone, put the new cone on the pin, and tie the new thread to the old tail with a small overhand knot. Raise the presser foot, loosen the tension dials, and pull the old thread out at the needle or looper end until the knot travels through the path.
Looper threads can be pulled all the way through, knot and all. Needle threads cannot, because the knot will not fit the eye. Pull the needle thread down until the knot reaches just above the needle, snip the knot off, and thread the eye by hand.
When You Do Have to Start Over
Thread breaks mid seam, a cone runs out, or a thread pops out of a tension disc. In those cases unthread back to the break and rethread that one path, but if the lower looper is the path that broke, unthread both needles first, thread the lower looper, and then rethread the needles. The order rule still applies.
Frequently Asked Questions
What order do you thread a serger in? Lower looper, upper looper, right needle, left needle. The loopers cross under the plate, so threading the upper looper first traps the lower looper thread on the wrong side and the stitch cannot form.
Do I have to rethread when I change thread color? No. Tie the new thread to the old tail above the cone, loosen the tensions, raise the presser foot and pull the knots through. Snip the knot before the needle eye and thread that one by hand.
Why does my chain fall apart as soon as I sew? Usually the looper order, sometimes a thread that never seated in its tension disc. Rethread the loopers in order with the presser foot up, and check that each thread clicks into the disc rather than sitting on top of it.
Should the presser foot be up or down when threading? Up. The tension discs only open when the foot is raised, and a thread laid across closed discs will look threaded and behave like it has no tension at all.
Can I use ordinary sewing thread on the cones? For a test, yes. For real projects, no. Regular spools run out quickly, they do not feed evenly from a horizontal pin, and all purpose thread is heavier than cone thread, which bulks up the seam. There is more on this in our serger thread guide.
The machine chains in the air but skips on fabric. Now what? That points at the needle or the tension rather than the threading. Fit a fresh needle of the correct type and check that both needle threads are in their discs, then work through the skipped stitch checklist.
The Bottom Line
Threading a serger is a fixed sequence, not a knack. Presser foot up, lower looper, upper looper, right needle, left needle, then a test chain before the fabric goes anywhere near the knife. Learn the tie on method on the first color change and the whole subject stops being the reason the machine stays in the box. Read next: our serger buying guide, the easiest sergers to thread and the Brother 1034D review.