In this scoping review, we aimed to comprehensively clarify the methodology of Mental practice (MP) by systematically mapping studies documenting the application of MP to post-stroke paralytic upper-extremity function. Specifically, when is an MP intervention most commonly applied after stroke onset? What is the corresponding MP load (intervention time, number of intervention days, and intervention period)? What are the most common methods of Motor Imagery (MI) recall and MI tasks used during the application of MP? Is MP often used in conjunction with individual rehabilitation? What are the paralyzed side’s upper-limb and cognitive function levels at the start of an MP intervention? The research questions were identified according to PRISMA-ScR. The PubMed, Scopus, Medline, and Cochrane Library databases were used to screen articles published until 19 July 2022. In total, 694 English-language articles were identified, of which 61 were finally included. Most of the studies were conducted in the chronic phase after stroke onset, with limited interventions in the acute or subacute phase. The most common intervention time was ≤30 min and intervention frequency was 5 times/week in MP. An audio guide was most commonly used to recall MI during MP, and 50 studies examined the effects of MP in combination with individual rehabilitation. The Fugl-Meyer Assessment mean for the 38 studies, determined using the Fugl-Meyer Assessment, was 30.3 ± 11.5. Additional research with the aim of unifying the widely varying MP methodologies identified herein is warranted.