Skilled, sequential movements can be acquired explicitly or implicitly. In the present study, we examined the effects of explicit knowledge obtained through instruction or spontaneous detection on transfer of visuomotor sequence learning. In the first session, participants learned a visuomotor sequence by trial and error. In subsequent sessions, the sequence was changed according to specific rules. Some participants received explicit instruction about which specific rules changed, while the others did not. Knowledge of changes via explicit instruction led to slower performance with fewer errors; the sluggishness persisted even in the last phase of transfer learning. On the other hand, knowledge discovered independently by the participants produced slower performance in the initial phase of learning with fewer errors, but their performance speed eventually reached the same level as that of the unaware participants. These results suggest that explicit knowledge may help to reduce errors in the initial phase of visuomotor sequence learning but may interfere with increasing speed, particularly when the knowledge is given rather than found.