Primary motor cortex (M1) and dorsal striatum are crucial for motor learning and maintenance of learned behavior. During motor learning, motor representations of corticostriatal ensembles are formed. Layer 5a (L5a), which connects M1 to the ipsi- and contra-lateral dorsal striatum, should be a key layer in the coordinated reorganization of M1 and the dorsal striatum for motor learning. M1 L5a neurons represent movement-related activity in the late stage of learning. However, it is unclear whether this activity is retained as a memory engram. Here, using Tlx3-Cre male transgenic mice, we performed two-photon calcium imaging of striatum-projecting L5a intratelencephalic (IT) neurons in forelimb M1 during late sessions of a self-initiated lever-pull task, and in sessions after 6 days of non-training following the late sessions. We found that before and after the non-training days, trained male animals showed stable motor performance. At the same time, we found that M1 L5a IT neurons strongly represented the well-learned forelimb movement, but not the unlearned orofacial movements. A subset of M1 L5a IT neurons consistently coded the well-learned forelimb movement before and after the non-training days. The inactivation of M1 IT neurons after learning impaired the performance of the task when the lever was made heavier or when the target range of the pulling distance was reduced. These results suggest that a subset of M1 L5a IT neurons persistently represent skilled movements after learning and are involved in fine-tuning the kinematics of well-learned movements.