This study reports the results of a qualitative study involving a large and longstanding online nurse listserv in the United States. A sample of 27 critical care and advanced-practice nurse practitioners was interviewed using semi-structured individual interviews. This study found evidence that participation in an online listserv offers a viable avenue for the continuous professional development of nurses by providing nurses the opportunity to make more informed decisions about their professional practice and keeping abreast with up-to-date changes in their specialty areas when they shared knowledge with one another. Follow-up interviews with 10 nurses who frequently shared their knowledge revealed six motivators that helped promote knowledge sharing: (a) reciprocity, (b) collectivism, (c) personal gain, (d) respectful environment, (e) altruism, and (f) technology. Implications for sustaining knowledge sharing in an online listserv are discussed. The finding will inform educators and administrators who support continuing education and professional development of healthcare professionals.