Inconsistent results are observed in the effects of transcranial direct current stimulation (tDCS) with different montages on motor learning. This study aimed to compare the effects of anodal and cathodal tDCS over primary motor cortex (M1) at different intensities (1 and 2 mA) on motor learning in healthy young adults. The participants were randomly divided to five groups: 1) 1mA M1 c-tDCS, 2) 1mA M1 a-tDCS, 3) 2 mA M1 c-tDCS, 4) 2 mA M1 a-tDCS and 5) M1 sham tDCS. The groups received 20-minute stimulation concurrent with serial response time test (SRTT) implicitly, while the tDCS was turned off after 30 seconds in the sham tDCS group. Response time (RT) and error rate (ER) during SRTT were assessed prior, during and 72 hours after the intervention. The results indicated that online learning occurred in all groups (P < 0.05), except in M1 c-tDCS (1 mA) (P>0.05). In addition, offline learning was observed in 1 mA M1 a-tDCS, 2mA M1 a-tDCS and 2 mA M1 c-tDCS as compared to sham tDCS and M1 c-tDCS (1 mA) groups (P < 0.05). On the other hand, 1 mA M1 c-tDCS group did not indicate any consolidation effect and even a trend toward negative offline learning. M1 a-tDCS with different intensities and also 2 mA M1 c-tDCS may be helpful for the enhancement of motor learning in young adults. Considering the deterioration effect of 1 mA M1 c-tDCS, it seems that caution should be applied in using it to improve motor learning.