Consolidation processes taking place between practice sessions are known to stabilize motor skills and improve performance without further practice (Trempe & Proteau, 2012). The recent consolidation theory also suggests that motor skills should be practiced in isolation from one another to minimize interference between the skills and optimize learning (Walker et al., 2003). This suggestion however challenges one of the most prominent theories of the 20th century suggesting that random practice (i.e., practicing two different skills alternatively during the same practice session) leads to better learning than blocked practice (i.e., practicing two different motor skills separately; Shea & Morgan, 1979). To address this discrepancy, we used a finger-sequence task in which participants had to learn in the same practice session two different sequences of finger movements. Participants either practiced the sequences in alternate order (random practice group) or separately (blocked practice group) before being retested 24 hours later. A control group also practiced only one sequence. As in previous reports, consolidation effects were measured by comparing the number of successfully completed sequences at the end of the practice session with the number of successfully completed sequences during the retention test (Walker et al., 2003). Our results revealed that the blocked practice schedule led participants to perform both sequences significantly faster during the retention test, whereas the random practice schedule led to a speed improvement of the first sequence only. Thus, random practice impaired the consolidation of the second sequence.