According to Real Simple Magazine, fleece sweatshirts require extra care in the laundry to keep them soft and to avoid pills and static. Properly washing sweatshirts requires a washing machine and a gentle laundry detergent.
Turn the sweatshirt inside out
Washing the garment inside out protects the finish or nap of the outside of the garment during the washing process. Zip any zippers to keep them from snagging on other items in the wash.
Wash with similar items
Place the sweatshirt in the washing machine with items in a similar color family to prevent color transfer. Also, avoid adding towels or other high-lint items. Fleece attracts lint.
Use a mild detergent
Mild laundry detergent is gentle on fleece and prevents pills from forming. Use the manufacturer's recommended amount of detergent, and wash at the temperature recommended on the garment's care tag. Avoid using fabric softener to preserve any water-resistant properties in the sweatshirt fabric.
Run an extra rinse cycle
Run an extra rinse cycle after the first one is complete. An extra rinse removes every trace of detergent for softer fleece.
Reshape the sweatshirt on a sweater drying rack, and allow it to air dry. Air drying is gentler than machine drying, and it helps the fleece remain soft.