A bone marrow aspiration device and associated method includes an introducer needle assembly and an aspiration needle assembly. The introducer needle assembly includes an introducer cannula having proximal and distal ends, each end including an opening, and a screw assembly coupled to the introducer handle. The screw assembly includes a threaded tube and a lead screw receivable in the threaded tube. An outer cover is disposed around and in sealing engagement with the threaded tube and the lead screw. The aspiration needle assembly is receivable in the introducer cannula and includes an aspiration cannula forming a channel for aspirating bone marrow and including a flexible portion that extends from a distal end along a length of the aspiration cannula. A length of the aspiration cannula that extends beyond the distal end of the introducer cannula is adjustable by advancing the lead screw into or reversing the lead screw out of the threaded tube.