Knit Fibers Behave Differently Than Regular Fabric

A knit pet sweater is built from looped fibers rather than woven threads, which is exactly what gives it that stretchy, cozy feel — but that same structure makes it more prone to stretching out of shape, pilling, or shrinking if it's washed the way you'd wash a t-shirt. Knowing how to wash a knit pet sweater properly is the difference between a sweater that lasts through several winters and one that's misshapen or bald in patches by January.

Before You Wash: Deal With Loose Fur and Debris

Pet sweaters accumulate shed fur, dirt, and the occasional bit of yard debris fast, and running a sweater through the wash with all of that still embedded just redistributes it and can clog up the machine's filter over time. Shake the sweater out thoroughly and run a lint roller or soft brush over it before washing to remove loose fur first — it makes the actual wash more effective and keeps your machine cleaner in the process.

Hand Washing: The Safest Option for Delicate Knits

For sweaters made from wool blends or looser knit patterns, hand washing in cool or lukewarm water with a mild, gentle detergent is the lowest-risk method. Submerge the sweater, gently press soapy water through the fibers without twisting or wringing, then rinse thoroughly in clean water until no soap remains. Wringing or twisting a wet knit is one of the fastest ways to stretch it permanently out of shape, so resist the urge and instead press out excess water gently between two towels.

Machine Washing: When It's Safe and How to Do It Right

Sturdier acrylic or cotton-blend knits can often go in the washing machine, but only on a gentle or delicate cycle with cold water, and ideally inside a mesh laundry bag to prevent stretching and snagging against a machine's agitator or other items in the load. Skip fabric softener, which can coat and stiffen synthetic knit fibers over time, and always check the specific care instructions for the sweater's exact fiber content before assuming it's machine-safe, since wool and wool blends generally are not.

Drying Without Ruining the Shape

This is where most knit sweaters actually get damaged, more often than in the wash itself. Heat from a dryer causes wool and many synthetic knit blends to shrink or felt, and even air-drying on a hanger can stretch a wet knit out of shape under its own weight. The safest method is to lay the sweater flat on a clean, dry towel, gently reshape it to its original dimensions, and let it air dry completely undisturbed, flipping it periodically so both sides dry evenly. This takes longer than tossing it in the dryer, but it's the single biggest factor in whether a knit sweater keeps its shape wash after wash.

Storing Knit Sweaters Between Seasons

Fold rather than hang knit sweaters for storage, since hanging allows gravity to stretch the shoulders and neckline over time. Store them clean and completely dry in a breathable container to prevent moisture buildup, and consider a cedar sachet or lavender pouch if wool moths are a concern in your area, since food residue and pet dander left on an unwashed sweater can attract them during off-season storage.

A little extra care at wash time pays off in a sweater that keeps its fit, its softness, and its shape through an entire season of wear rather than one or two washes.