Concerns with the retention of women in engineering have led to the implementation of numerous programs to improve retention, including mentoring programs. The college of engineering at Washington State University (WSU) started a novel women's mentoring program in 2008, using professional engineers who graduated from WSU as mentors. The program is purely voluntary, and has grown from 30 mentors and 38 mentees in 2008 to 61 mentors and 90 mentees in 2011 (many mentors are willing to be paired up with more than one student). Preliminary results indicate that participants in the mentoring program are retained at a higher rate than students that do not participate; of the 42 freshmen entering WSU in the fall of 2010 and participating in the program, 74% have stayed in engineering compared to 68% for all 54 female freshman students. In past years (2003-2009), an average of 51% of female students are still in engineering at the end of their freshman year. This paper presents a model for a self-sustaining, effective women's mentoring program that has the potential to improve retention rates of women in engineering.