A method and an apparatus for stuffer box crimping a multifilament yarn, wherein the yarn being processed is pneumatically advanced by means of a conveying fluid into a stuffer box chamber and compacted to a yarn plug, with the conveying fluid leaving the stuffer box chamber through openings and being removed by suction. To be able to influence the yarn plug formation mainly by the suction stream, the invention provides for constructing the source of vacuum as an injector, which connects to a source of pressure via a pressure connection and to a suction line via a suction connection that precedes in the direction of the flow. As a result, the suction stream of the conveying fluid is generated by a compressed air stream, with the compressed air stream and the suction stream being jointly discharged as a common airflow.