The final finishing of yarn-dyed fabric refers to processes such as singeing, desizing, scouring, mercerizing, bleaching and optical brightening.

Because of their different chemical structures, vat dyes differ in chemical performance: some cannot withstand alkaline boiling (e.g. sulfur indigo red B); some cannot withstand mercerizing (e.g. RSN blue); some cannot withstand bleaching (e.g. RSN blue, bromoindigo). Yarn-dyed fabrics made with these dyes are therefore not suitable for final finishing.

Vat dyes with good resistance to strong alkali and good fastness to bleaching should be selected. However, some vat dyes change shade after mercerizing and chlorine bleaching in final finishing (for example RSN blue turns dark green). If treated with a dilute hydrosulfite solution, the original bright blue can be restored, so RSN blue can sometimes be used for final finishing, but an additional hydrosulfite treatment step is needed. Otherwise, vat blue BC with good fastness to bleaching can be substituted, though it is more expensive.

When dyeing yarn with reactive dyes, a lot of dust is often seen during drying, and even a white powdery layer on the yarn. This is related to the dye and auxiliaries used; selecting suitable dyes and controlling the drying temperature reduce the problem.