The purpose of the study was to determine the effects of tool-assisted massage and passive stretching on hamstring flexibility. Twenty-one healthy college baseball players (age = 20.2 ± 1.5 yrs, height = 181.4 ± 5.9 cm, mass = 82.5 ± 8.5 kg) participated in the study. The participants were randomly assigned to 1 of the following 3 groups: passive stretching (PAS, n = 6); passive stretch and tool-assisted friction massage (FUZ, n = 7); or control (CON, n = 8). The interventions took place 6 days a week for 3 weeks, Sunday through Friday, for a period of 18 days on both legs. The PAS group received 3, 30-second repetitions of passive hip flexion with the knee fully extended. The FUZ group received the PAS group stretching treatment plus a 5-minute tool-assisted friction massage, 2 times a week for 6 treatments (2 days rest between treatment days). The participants’ hamstring flexibility was measured employing the passive knee extension test. The baseline knee extension angle (KEA) was measured 1 day prior to the first stretching session day on both legs, and KEA was measured again on the day after the last stretching session to determine outcome difference. At baseline, there were no significant differences in the right leg (RL) between groups (PAS vs. FUZ, p = .957; PAS vs. CON, p = .713; FUZ vs. CON, p = .509) and left leg (LL) for the KEA measurement. Post data indicated a significant increase in hamstring flexibility for the PAS (RL, p = .001; LL = .001) and FUZ group (RL, p = .001; LL, p = .001). However, there were no significant differences in hamstring flexibility between the PAS and FUZ group for either the right or left leg (RL, p = .789; LL, p = 0.590). While passive stretching is an effective method to increase hamstring flexibility, in this sample the use of tool-assisted massage in conjunction with passive stretching did not provide additional hamstring flexibility. This may be due to number of repetitions, duration, or frequency of stretching and application of tool-assisted massage protocol of the treatment.