The answer depends on the type of diapers you are buying and for whom:
Generally no . The IRS considers standard infant diapers personal care items rather than medical expenses because incontinence is a normal part of infant development. Exceptions for Children: can i buy diapers with fsa
Many brands like Goodnites are FSA-eligible because they are used to manage bedwetting, which can be considered an incontinence issue in older children. The answer depends on the type of diapers