The purpose of this study was to determine the effects of tool-assisted massage and passive stretching on hamstring flexibility. The hamstring is the most commonly injured multijoint muscle group in the body. To decrease the incidence of hamstring injury, clinicians employ the use of passive stretching to treat muscle shortening. Participants included male college baseball players between the ages of 18 and 24 years (n = 21). Utilizing three study groups, the participants' hamstring flexibility was measured by employing the passive knee extension test. Measurements of hamstring flexibility were taken prior to the study intervention and after the study intervention. The results indicated a significant increase in hamstring flexibility for the passive stretching and Fuzion groups, alpha = .05, p < .001. There was not a significant difference in hamstring flexibility between the passive stretching and Fuzion groups for the right and left leg, respectively, p = .789, p = .590. We concluded that, although passive stretching is an effective method to increase hamstring flexibility, the use of tool-assisted massage in conjunction with passive stretching does not significantly enhance hamstring flexibility.