The aim of this study was to characterize relationships between anthropometric and isoinertial strength characteristics and bowling speed in junior and senior cricket fast bowlers. Subjects were first-class senior (n = 24; mean ± SD age = 23.9 ± 4.8 years, height = 187.4 ± 4.8 cm, mass = 87.8 ± 8.4 kg) and junior representative (n = 48; mean ± SD age = 14.8 ± 1.3 years, height = 175.7 ± 9.8 cm, mass = 65.8 ± 12.9 kg) male fast bowlers. A full anthropometric profile, upper-and lower-body isoinertial strength tests, and peak bowling speed (Vpeak) were assessed on the same day. The senior bowlers had a substantially faster Vpeak (126.7 km·h−1) than the juniors (99.6 km·h−1), a larger estimated muscle mass (seniors 40.0 ± 3.9 kg, juniors 28.3 ± 5.6 kg), and a greater bench press throw and deltoid throw (all p < 0.01). The best multiple predictors of Vpeak for the junior bowlers were the static jump, bench throw, body mass, percentage muscle mass, and height (multiple-correlation r = 0.86). For the senior bowlers, static jump and arm length correlated positively with Vpeak (multiple-correlation r = 0.74). The 1-legged countermovement jump was negatively correlated with Vpeak in both groups. We conclude that differences in Vpeak between junior and senior bowlers relate primarily to body mass and upper-body strength. However, lower body strength is a more important contributor to Vpeak in senior bowlers.