Breast pump adapter, breast pump system, and adapter kit are provided, as well as a method of using same. The adapter allows coupling of a breast shield assembly with a storage container (e.g., milk bottle), with an airtight, sealed fluid path. Compatibility of a bottle coupling of the breast shield assembly with a milk bottle, for example, is not necessary with the adapter. The breast pump adapter can include an elongated body having a first end and a second end and an intermediate central region. At least one of the first and second ends can be formed of a flexible material configured to stretch around a breast shield assembly bottle coupling or around a storage container opening to form an airtight seal. A housing can optionally be included as part of a breast pump adapter kit.
