In the United States, the 2.4-km run is arguably the most common law enforcement aerobic assessment. Potential limitations are that recruits use an internal pacing strategy, the test requires fewer direction changes, and less-fit recruits run for longer. The 20-m multistage fitness test (20MSFT) is commonly used internationally to assess aerobic fitness in law enforcement recruits and provides an external pacing strategy. This study documented sex differences between the 2.4-km run and 20MSFT in law enforcement recruits, and between-test relationships. Retrospective analysis on 8 academy classes (463 men and 87 women) from 1 agency was conducted. The 20MSFT was completed before academy and the 2.4-km run in the first week. Between-sex comparisons in the 2.4-km run and 20MSFT were conducted with independent-samples t-tests and effect sizes. Estimated V[Combining Dot Above]O2max from the tests was compared with paired-samples t-tests. Correlations and linear regression calculated 2.4-km run and 20MSFT relationships. There were significant between-sex differences for the 2.4-km run and 20MSFT (p < 0.01), with moderate (d = 0.9) and small (d = 0.4) effects, respectively. Estimated 2.4-km run V[Combining Dot Above]O2max was greater than that from the 20MSFT (p < 0.01). The 2.4-km run had significant relationships with the 20MSFT (r = -0.6), although the regression equations were low (r = 0.30-0.37). Between-sex differences in the 20MSFT seemed less than for those in the 2.4-km run. Nonetheless, even with significant relationships between the tests, the 20MSFT induces a higher running intensity and direction changes. This may limit transferability with the 2.4-km run in law enforcement recruits.